Full-color image-forming method

ABSTRACT

Provided are a toner containing at least a binder resin and a colorant, the toner having a specific hue angle and an absorbance at a specific wavelength in reflectance spectrophotometry, and a full-color image-forming method involving the use of the toner, the method including the steps of: forming an electrostatic image on a charged electrostatic image bearing member; developing the formed electrostatic image with the toner to form a toner image; transferring the formed toner image onto a transfer material; and fixing the transferred toner image to the transfer material to form a fixed image.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a toner for developing an electrostaticimage in an image-forming method such as electrophotography orelectrostatic printing, or a toner for forming a toner image in afull-color image-forming method based on a toner-jet system, andparticularly, to a toner to be used in a fixing system in which a tonerimage is fixed to a transfer material such as a print sheet under heatand pressure. The present invention relates also to an image-formingmethod based on a full-color electrophotographic system to be employedin, for example, a copying machine, a printer, a facsimile, or a digitalproof.

2. Description of the Related Art

Various methods have been conventionally known as electrophotographicmethods. A general electrophotographic method is as described below. Thesurface of a latent image bearing member composed of a photoconductivematerial is uniformly charged by, for example, corona charging or directcharging with a charging roller or the like, and then an electricallatent image is formed on the latent image bearing member by, forexample, the application of light energy. Next, the electrical latentimage is developed with positively or negatively charged toner so that atoner image is formed. After the toner image has been transferred onto atransfer material such as paper as required, the toner image is fixedonto the transfer material with heat, a pressure, or the like, whereby acopied article is obtained.

In recent years, the formation of an image having an additionally highresolution has been demanded of an image-forming apparatus based on anelectrophotographic method such as a printer or a copying machine. Inparticular, an electrophotographic color image-forming apparatus hasbeen finding use in miscellaneous applications as the apparatus hasbecome widespread, and the demands made upon the apparatus for imagequality have become more severe. That is, the color image-formingapparatus has been required to reproduce even a fine portion extremelyfinely and faithfully in the print of an image such as a generalphotograph, catalogue, or map. In addition, the apparatus has beenrequired to improve the definition of the color of an image and toextend the color reproduction range of the image.

Further, as for image quality, there are demands for forming anadditionally smooth image on a transfer material such as paper even whenthe transfer material has surface unevenness. In general, an imageformed by an electrophotographic method has a step difference between anon-image portion and an image portion in the direction perpendicular toa paper surface of 10 to 30 μm. In a full-color image, in addition to astep difference between a non-image portion and an image portion, a stepdifference in the image portion between a primary color and a secondarycolor in the direction perpendicular to a paper surface is 5 to 20 μm,which also causes a reduction in image quality.

In addition, the number of sheets to be printed has also been increasingin association with an increase in speed of an image-forming apparatus,so an additional reduction in running cost has been demanded of theapparatus. Performance requested of toner is as follows: the tonerachieves an image with quality and definition each of which iscomparable to or higher than a conventional one without narrowing acolor reproduction range, a toner consumption is reduced, and fixingenergy is reduced.

To satisfy those demands, an increase in content of a colorant in tonerhas been proposed (see, for example, Patent Documents 1 to 4). Each ofthose documents aims to form an image with a smaller toner amount than aconventional one and to reduce the surface unevenness of the image byincreasing the content of a colorant in toner. However, an increase incolorant content of toner has involved the following problem: the peakof a characteristic absorption wavelength resulting from a colorant inthe reflection spectrum of an image becomes broad, with the result thatthe chroma and lightness of the image reduce.

There is employed a technology involving controlling the dispersed stateof a colorant in toner as a method of suppressing reductions in chromaand lightness of a toner image (see, for example, Patent Document 5).The control of the dispersed state of the colorant in the toner exerts acertain effect in some cases, but the control is still insufficient forforming of an image with small image unevenness while reducing the usageof the toner, and, in the case of the control, a reduction in chroma ofa secondary color is particularly remarkable.

As described above, no toner having the following characteristics hasbeen found yet: an image having a high resolution and high definition isachieved, good image quality is expressed while none of an image colorgamut, chroma, and lightness is reduced even in a secondary color, and arunning cost can be reduced.

Patent Document 1: 11-72960 A

Patent Document 2: 11-237761 A

Patent Document 3: 2002-131973 A

Patent Document 4: 2005-128537 A

Patent Document 5: 2003-280723 A

SUMMARY OF THE INVENTION

An object of the present invention is to solve the above problems of therelated art.

That is, the object of the present invention is to provide a cyan toner,a magenta toner, a yellow toner, and a black toner each enabling theformation of a good image which: achieves a resolution and definitioneach of which is higher than a conventional one; shows a good imagecolor gamut, good chroma, and good lightness even in a secondary color;and has small surface unevenness, and a full-color image-forming methodinvolving the use of any one of the toners.

The present invention relates to a cyan toner, including at least: abinder resin; and a colorant, in which the cyan toner has a value(h*_(C)) for a hue angle h* based on a CIELAB color coordinate system of210.0 to 270.0, an absorbance (A_(C470)) at a wavelength of 470 nm of0.300 or less, an absorbance (A_(C620)) at a wavelength of 620 nm of1.500 or more, and a ratio (A_(C620)/A_(C670)) of A_(C620) to anabsorbance (A_(C670)) at a wavelength of 670 nm of 1.00 to 1.25 inreflectance spectrophotometry.

Further, the present invention relates to a magenta toner, including atleast: a binder resin; and a colorant, in which the magenta toner has avalue (h*_(M)) for a hue angle h* based on a CIELAB color coordinatesystem of 330.0 to 30.0, an absorbance (A_(M570)) at a wavelength of 570nm of 1.550 or more, an absorbance (A_(M620)) at a wavelength of 620 nmof 0.250 or less, and a ratio (A_(M570)/A_(M450)) of A_(M570) to anabsorbance (A_(M450)) at a wavelength of 450 nm of 1.80 to 3.50 inreflectance spectrophotometry.

Further, the present invention relates to a yellow toner, including atleast: a binder resin; and a colorant, in which the yellow toner has avalue (h*_(Y)) for a hue angle h* based on a CIELAB color coordinatesystem of 75.0 to 120.0, an absorbance (A_(Y450)) at a wavelength of 450nm of 1.600 or more, an absorbance (A_(Y470)) at a wavelength of 470 nmof 1.460 or more, and an absorbance (A_(Y510)) at a wavelength of 510 nmof 0.500 or less in reflectance spectrophotometry.

Further, the present invention relates to a black toner, including atleast: a binder resin; and a colorant, in which the black toner has avalue (c*_(K)) for c* based on a CIELAB color coordinate system of 20.0or less, an absorbance (A_(K600)) at a wavelength of 600 nm of 1.610 ormore, and a ratio (A_(K600)/A_(K460)) of A_(K600) to an absorbance(A_(K460)) at a wavelength of 460 nm of 0.970 to 1.035 in reflectancespectrophotometry.

Further, the present invention relates to a full-color image-formingmethod, including the steps of: forming electrostatic images on acharged electrostatic image bearing member; developing the formedelectrostatic images with toners to form toner images; transferring theformed toner images onto a transfer material; and fixing the transferredtoner images to the transfer material to form fixed images, in which:the step of forming the toner images includes a step of performingdevelopment with a first toner selected from a black toner, a cyantoner, a magenta toner, and a yellow toner to form a first toner image,a step of performing development with a second toner except the firsttoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a second toner image, a step of performingdevelopment with a third toner except the first toner and the secondtoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a third toner image, and a step ofperforming development with a fourth toner except the first toner, thesecond toner, and the third toner selected from the black toner, thecyan toner, the magenta toner, and the yellow toner to form a fourthtoner image; and the cyan toner contains at least a binder resin and acolorant, and has a value (h*_(C)) for a hue angle h* based on a CIELABcolor coordinate system of 210.0 to 270.0, an absorbance (A_(C470)) at awavelength of 470 nm of 0.300 or less, an absorbance (A_(C620)) at awavelength of 620 nm of 1.500 or more, and a ratio (A_(C620)/A_(C670))of A_(C620) to an absorbance (A_(C670)) at a wavelength of 670 nm of1.00 to 1.25 in reflectance spectrophotometry.

Further, the present invention relates to a full-color image-formingmethod, including the steps of: forming electrostatic images on acharged electrostatic image bearing member; developing the formedelectrostatic images with toners to form toner images; transferring theformed toner images onto a transfer material; and fixing the transferredtoner images to the transfer material to form fixed images, in which:the step of forming the toner images includes a step of performingdevelopment with a first toner selected from a black toner, a cyantoner, a magenta toner, and a yellow toner to form a first toner image,a step of performing development with a second toner except the firsttoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a second toner image, a step of performingdevelopment with a third toner except the first toner and the secondtoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a third toner image, and a step ofperforming development with a fourth toner except the first toner, thesecond toner, and the third toner selected from the black toner, thecyan toner, the magenta toner, and the yellow toner to form a fourthtoner image; and the magenta toner is a magenta toner containing atleast a binder resin and a colorant, and the magenta toner has a value(h*_(M)) for a hue angle h* based on a CIELAB color coordinate system of330.0 to 30.0, an absorbance (A_(M570)) at a wavelength of 570 nm of1.550 or more, an absorbance (A_(M620)) at a wavelength of 620 nm of0.250 or less, and a ratio (A_(M570)/A_(M450)) of A_(M570) to anabsorbance (A_(M450)) at a wavelength of 450 nm of 1.80 to 3.50 inreflectance spectrophotometry.

Further, the present invention relates to a full-color image-formingmethod, including the steps of: forming electrostatic images on acharged electrostatic image bearing member; developing the formedelectrostatic images with toners to form toner images; transferring theformed toner images onto a transfer material; and fixing the transferredtoner images to the transfer material to form fixed images, in which:the step of forming the toner images includes a step of performingdevelopment with a first toner selected from a black toner, a cyantoner, a magenta toner, and a yellow toner to form a first toner image,a step of performing development with a second toner except the firsttoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a second toner image, a step of performingdevelopment with a third toner except the first toner and the secondtoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a third toner image, and a step ofperforming development with a fourth toner except the first toner, thesecond toner, and the third toner selected from the black toner, thecyan toner, the magenta toner, and the yellow toner to form a fourthtoner image; and the yellow toner is a yellow toner containing at leasta binder resin and a colorant, and the yellow toner has a value (h*_(Y))for a hue angle h* based on a CIELAB color coordinate system of 75.0 to120.0, an absorbance (A_(Y450)) at a wavelength of 450 nm of 1.600 ormore, an absorbance (A_(Y470)) at a wavelength of 470 nm of 1.460 ormore, and an absorbance (A_(Y510)) at a wavelength of 510 nm of 0.500 orless in reflectance spectrophotometry.

Further, the present invention relates to a full-color image-formingmethod, including the steps of: forming electrostatic images on acharged electrostatic image bearing member; developing the formedelectrostatic images with toners to form toner images; transferring theformed toner images onto a transfer material; and fixing the transferredtoner images to the transfer material to form fixed images, in which:the step of forming the toner images includes a step of performingdevelopment with a first toner selected from a black toner, a cyantoner, a magenta toner, and a yellow toner to form a first toner image,a step of performing development with a second toner except the firsttoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a second toner image, a step of performingdevelopment with a third toner except the first toner and the secondtoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a third toner image, and a step ofperforming development with a fourth toner except the first toner, thesecond toner, and the third toner selected from the black toner, thecyan toner, the magenta toner, and the yellow toner to form a fourthtoner image; and the black toner is a black toner containing at least abinder resin and a colorant, and the black toner has a value (c*_(K))for c* based on a CIELAB color coordinate system of 20.0 or less, anabsorbance (A_(K600)) at a wavelength of 600 nm of 1.610 or more, and aratio (A_(K600)/A_(K460)) of A_(K600) to an absorbance (A_(K460)) at awavelength of 460 nm of 0.970 to 1.035 in reflectance spectrophotometry.

According to the present invention, a toner consumption can be reduced,and an image having a color gamut comparable to or better than aconventional one not only in a primary color but also in a secondarycolor can be formed. In addition, a good-appearance image with reducedsurface unevenness can be obtained, and a running cost can besuppressed.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a steric conceptual view of a CIELAB color coordinate system.

FIG. 2 is a view showing coordinates.

FIG. 3 is a view showing the outline of a structure of an example of animage-forming apparatus to be used in the present invention.

FIG. 4 is an outline view showing an example of a fixing apparatus to beused in the present invention.

FIG. 5 is an outline view showing another example of the fixingapparatus to be used in the present invention.

FIG. 6 is a view showing an example in which the measurement of a glasstransition point (Tg), a temperature of a highest endothermic peak,endotherm, and half width of the highest endothermic peak of the toner,to be used in the present invention, is performed for Toner 1.

FIG. 7 is a view showing the outline of a constitution of an example ofa surface modification apparatus to be suitably used upon production ofa toner of the present invention.

FIG. 8 is a view showing a dispersion rotor of the apparatus shown inFIG. 7 and the arrangement of square disks provided on the rotor.

FIG. 9 are each a view showing an example of a binarizing approach forgradation reproduction employed in the present invention.

FIG. 10 is a view showing an example of a dither pattern of each coloremploying the binarizing approach employed in the present invention.

FIG. 11 is a view showing the outline of a charge quantity measuringapparatus for a two-component developer used in the present invention.

FIG. 12 are each view showing an example of an arrangement of thelattice points of the dither pattern used in the present invention.

FIG. 13 is a view showing the concept of dot spread.

FIG. 14 is a view showing the concept of dot chipping.

DESCRIPTION OF REFERENCE SYMBOLS

-   -   4 heating device    -   5 heat-resistant film    -   6 temperature detecting element    -   7 ceramic heater    -   8 rubber roller    -   9 mandrel    -   10 pressure roller (pressure member)    -   11 fixing belt    -   12 pressure roller (pressure member)    -   13 excitation coil    -   14 core    -   15 holder    -   16 temperature sensor    -   17 transport guide    -   18 separation claw    -   19 elastic layer    -   20 metal conductor    -   21 hollow mandrel    -   22 surface releasable heat-resistant elastic layer    -   41 classifying rotor    -   42 fine powder collection discharge port    -   43 raw material supply port    -   44 liner    -   45 cold air introduction port    -   46 dispersing rotor    -   47 powder discharge port    -   48 discharge valve    -   49 guide ring    -   50 square disk    -   51 first space    -   52 second space    -   55 casing    -   100 heat pressure fixing unit    -   101 manuscript    -   102 manuscript board glass    -   103 exposure lamp    -   104 lens    -   105 full-color sensor    -   106 photosensitive drum    -   107 pre-exposure lamp    -   108 corona charging device    -   109 laser exposure optical system    -   109 a polygon mirror    -   109 b lens    -   109 c mirror    -   111Y yellow developing device    -   111C cyan developing device    -   111M magenta developing device    -   111K black developing device    -   112 means for detecting light on drum    -   113 transferring device    -   113 a transferring drum    -   113 b transfer charging device    -   113 c adsorption charging device    -   113 d inner charging device    -   113 e outer charging device    -   113 f transfer sheet    -   113 h separation charging device    -   113 g adsorbing roller    -   114 cleaning device    -   115Y yellow eccentric cam    -   115C cyan eccentric cam    -   115M magenta eccentric cam    -   115K black eccentric cam    -   116 a, 116 b, 116 c cassette    -   117 a separation claw    -   117 b separation pushup roller    -   118 tray    -   201 screen    -   202 measurement container    -   203 lid    -   204 sucking machine    -   205 suction port    -   206 air flow control valve    -   207 vacuum gauge    -   208 potentiometer    -   209 capacitor    -   E optical image

DESCRIPTION OF THE EMBODIMENTS

A CIELAB color coordinate system used in the present invention is aspecification specified by Commission Internationale de l'Eclairage(CIE). The system is specified also in JIS 28729, and is generally usedas means useful in representing a color by digitizing the color. FIG. 1shows a steric conceptual view of the CIELAB color coordinate system. InFIG. 1, horizontal axes a* and b* both represent hue. The hue measures atone such as red, yellow, green, blue, and violet. In the presentinvention, the a* axis represents a red-green direction and the b* axisrepresents a yellow-blue direction. A vertical axis L* representslightness, showing a degree of color lightness comparable irrespectiveof the hue. Further, the c* value represents chroma, showing a degree ofvividness of color, and is determined using the following formula.c*=√{square root over (a* ² +b* ²)}  [formula 1]

As shown in FIG. 2, a hue angle h* is an angle formed between a straightline connecting a hue (a*, b*) and the origin and a positive a* axis, oris an angle formed between the straight line and the positive a* axis inthe counterclockwise direction from the positive a* axis. Accordingly, ahue angle of 0.0 and a hue angle of 360.0 mean the same hue angle. Inaddition, for example, the expression “hue angle is 330.0 to 30.0” asused in the present invention refers to a region obtained by merging ahue angle region of 330.0 to 360.0 and a hue angle region of 0.0 to30.0. The hue angle can represent a specific hue irrespective oflightness.

Next, a method for the reflectance spectrophotometry of toner in thepresent invention will be described. It should be noted that theemployment of the measurement method of the present invention allows thekind and content of a colorant in the toner, the dispersed state of thecolorant in the toner, and color development property derived from thecolor of a binder resin and the color of any other additive andintrinsic to the toner to be accurately determined.

A specific measurement method is as described below. The toner issufficiently dispersed in an aqueous solution of a nonionic surfactantso that the resultant toner dispersion liquid has a certainconcentration. A certain amount of the toner dispersion liquid ismeasured and taken, and the taken liquid is filtrated through a filterhaving a whiteness of 95 to 120 and a pore diameter of 0.2 to 1.0 μm sothat a certain amount of a toner layer is formed on the filter. Atransparent, thin glass plate A (cover glass for observation with anoptical microscope) is mounted on the upper portion of the toner layer.The resultant is mounted on a glass plate B (slide glass for observationwith an optical microscope) having a thickness of 1 to 2 mm, and,furthermore, a metallic weight is mounted from above the thin glass Amounted on the upper portion of the toner layer so that a certain loadis applied. The resultant is heated with a hot plate retained at 150° C.for 15 seconds, whereby a sample for measurement is obtained. Theabsorbance of the above sample for measurement at each wavelength ismeasured with a reflectance spectrophotometer capable of measuring anabsorbance in the wavelength range of 380 nm to 730 nm at an interval of10 nm by using a sample obtained by mounting the glass A on the filterto which no toner is caused to adhere as a reference.

According to the above method, when the toner melts, the toner adsorbsto the glass plate A to form a uniform toner layer, so the colordevelopment property of the toner can be stably measured irrespective ofvariations in fixing performance, particle diameter, and shape of thetoner.

For example, the following method can be employed as an additionallyspecific measurement method.

An aqueous solution is prepared by dissolving a nonionic surfactant (forexample, a Contaminon N manufactured by Wako Pure Chemical Industries,Ltd. can be used) in ion-exchanged water having an electric conductivityof 0.03 to 0.08×10⁴ S/m at a concentration of 3 mass %.

The true density of the toner is measured by a method to be describedlater, and is represented by ρ_(T) (g/cm³). 0.02×ρ_(T) (g) of the toneris measured and taken, and 250 g of the above aqueous solution aregently added to the measured toner, whereby a mixed liquid is prepared.At that time, attention should be paid in order that the aqueoussolution may not foam. The mixed liquid is subjected to a dispersiontreatment with an ultrasonic cleaning machine (for example, a UT-205S(manufactured by Sharp Corporation) can be used) for 10 minutes, wherebya toner dispersion liquid containing the toner sufficiently dispersed inthe mixed liquid is prepared.

A hydrophilic membrane filter having a whiteness of 95 to 120 and a porediameter of 0.2 to 1.0 μm (for example, a cellulose ester-type membranefilter A080047 (having a pore diameter of 0.80 μm) manufactured by ToyoRoshi Kaisha, Ltd. can be used) is set in a filter holder having acompatible filter diameter of 25 mm (an inner diameter of 18 mm). 8 mlof the toner dispersion liquid are measured and taken, and the takenliquid is gently charged into the filter holder. At that time, attentionshould be paid in order that the toner dispersion liquid may not foam.Next, the toner dispersion liquid is subjected to suction filtrationwith a suction apparatus such as an aspirator (for example, an AspiratorSP30 manufactured by Marcos-mepher can be used). After the suction hasbeen continued for 10 minutes, the filter is carefully taken out of thefilter holder, and the filter is dried at 40° C. for 3 days, whereby atoner-carrying sample is obtained on the filter.

The above sample is mounted on a glass plate B measuring 1 to 2 mm thickby 76 mm long by 26 mm wide (for example, a slide glass S1112manufactured by Matsunami Glass Ind., Ltd. can be used). Further, a thinglass plate A measuring 0.12 to 0.17 mm thick by 18 mm long by 18 mmwide (for example, a cover glass CT18189 manufactured by Matsunami GlassInd., Ltd. can be used) is gently mounted on the upper portion of thetoner layer. Further, a weight (for example, brass measuring 22 mm longby 22 mm wide by 42 mm high can be used) is mounted on the upper portionof the thin glass plate A so that a pressure of about 0.54 N/cm² isapplied. In the state, the resultant is left at rest and heated on a hotplate retained at 150° C. for 15 seconds, whereby a sample formeasurement is obtained. At that time, after the leaving at rest andheating, the weight and the glass plate B are immediately removed fromthe sample so that the temperature of the sample returns to normaltemperature as quickly as possible. Separately, the thin glass plate Ais mounted on the same membrane filter as that described above, and asample for reference is obtained in the same manner as in the abovesample.

A commercially available reflectance spectrophotometer can be used inthe reflectance spectrophotometry. To be specific, the absorbance ateach wavelength, L*, c*, and h* of the toner can be determined asfollows: the above reference sample is subjected to measurement with,for example, a SpectroScan Transmission (manufactured by GretagMacbeth)at the time of the calibration of the apparatus, and then the sample formeasurement is subjected to measurement. Specific measurement conditionsare shown below.

<Measurement Conditions>

Observation light source: D50

Observation view angle: 2°

Density: DIN NB

White reference: Pap

Filter: No (absent)

Measurement mode: Reflectance

Desired data out of values for CIE Lch(ab) (corresponding to L*, c*, andh* described above) and Spectrum D (corresponding to an absorbance ateach wavelength in the wavelength range of 380 nm to 730 nm) measuredunder the above measurement conditions is used.

First, a cyan toner will be described.

The cyan toner of the present invention includes at least: a binderresin; and a colorant, wherein the cyan toner has a value (h*_(C)) for ahue angle h* based on a CIELAB color coordinate system of 210.0 to270.0, an absorbance (A_(C470)) at a wavelength of 470 nm of 0.300 orless, an absorbance (A_(C620)) at a wavelength of 620 nm of 1.500 ormore, and a ratio (A_(C620)/A_(C670)) of A_(C620) to an absorbance(A_(C670)) at a wavelength of 670 nm of 1.00 to 1.25 in reflectancespectrophotometry.

The phrase “cyan toner has h*_(C) of 210.0 to 270.0 in the reflectancespectrophotometry” as used in the present invention means that the toneris a toner having a cyan color. When h*_(C) is less than 210.0, thetoner shows a color close to a green color. When h*_(C) exceeds 270.0,the toner shows a color close to a purple color. In addition, A_(C470),A_(C620), and A_(C620)/A_(C670) each show color development property ata specific absorption wavelength of cyan.

In the case of the cyan toner having h*_(C) within the above range, thelarger A_(C620), the larger opacifying power the cyan toner has; a cyanimage having a high image density can be formed with a small toneramount. The smaller A_(C470), the more excellent in color developmentproperty the cyan toner is; a cyan image having additionally largelightness can be formed with the same toner amount as that in the caseof a conventional toner. In addition, A_(C620)/A_(C670) is involved inthe tinge of the toner, and, when the ratio falls within the aboverange, a full-color image favorably expressing color developmentproperty even in a secondary color and having a good color space can beformed.

An increase in addition amount of the colorant in the cyan toner is aptto cause A_(C470) to have a large value. However, when A_(C470) exceeds0.300, the lightness of an image reduces so that the image becomesobscure even if a sufficient image density is obtained. Accordingly,when a full-color image is formed, a representable color space becomessmall. When A_(C620) is less than 1.500, a sufficient image densitycannot be obtained, or a toner amount on paper must be increased, soeffects of the present invention such as a reduction in unevenness ofthe surface of an image, an improvement in resolution of the image, anda reduction in toner consumption cannot be obtained. In addition, anincrease in addition amount of the colorant in the cyan toner is apt tocause A_(C620)/A_(C670) to have a small value. However, whenA_(C620)/A_(C670) exceeds 1.25, the cyan toner shows a strong yellowcolor, and an ability to represent a secondary color is as follows: acolor gamut near a purple color becomes small. When A_(C620)/A_(C670) isless than 1.00, the cyan toner shows a strong red color, and the abilityto represent a secondary color is as follows: a color gamut near a greencolor becomes small.

According to the present invention, the value for A_(C620) describedabove is preferably large because a toner amount on paper can bereduced, and the effects of the present invention become large. However,the value for A_(C620) described above is preferably 2.300 or less inconsideration of a color balance when a full-color image is formed bycombining the cyan toner with any other color toner such as a magentatoner, a yellow toner, or a black toner, the color developmentefficiency of the colorant of the cyan toner, and a material cost. Therange of A_(C620) described above is more preferably 1.550 to 2.200,still more preferably 1.650 to 2.200, or particularly preferably 1.800to 2.100.

The value for A_(C470) described above is preferably small because animage excellent in color development property, and having additionallylarge lightness and additionally large chroma can be formed. However,the value for A_(C470) described above is preferably 0.050 or more inconsideration of a color balance when a full-color image is formed bycombining the cyan toner with any other color toner such as a magentatoner or a yellow toner, the color development efficiency of thecolorant of the cyan toner, and a material cost. The range of A_(C470)described above is more preferably 0.050 to 0.250, still more preferably0.080 to 0.250, or particularly preferably 0.100 to 0.200.

The range of the value for A_(C620)/A_(C670) described above is morepreferably 1.00 to 1.20, still more preferably 1.03 to 1.18, orparticularly preferably 1.05 to 1.10. This is because a color balancebecomes good, and a balance between an increase in representable colorspace of an image and an improvement in resolution or a reduction insurface unevenness of the image becomes particularly suitable.

A_(C470), A_(C620), and A_(C670) described above can each be controlleddepending on, for example, the kind and addition amount of the colorantin the toner, the state of presence of the colorant in the toner, thestate of presence of any other additive or the like, and the color of anadditive.

A_(C670) described above is preferably 1.300 to 2.100. An increase inaddition amount of the colorant in the toner is apt to cause A_(C670) tohave a large value. When A_(C670) exceeds 2.100, the cyan toner is aptto show a strong red color, and an ability to represent a secondarycolor is as follows: a color gamut near a green color is apt to besmall. When A_(C670) is less than 1.300, the cyan toner is apt to show astrong yellow color, and the ability to represent a secondary color isas follows: a color gamut near a purple color is apt to be small.Accordingly, the range of the value for A_(C670) is more preferably1.350 to 2.000, or particularly preferably 1.600 to 1.950. This isbecause a color balance is particularly suitable, and the representablecolor space of an image becomes particularly large.

By the same reason as that described above, an absorbance (A_(C420)) ata wavelength of 420 nm is preferably 0.250 to 0.600. When A_(C420)exceeds 0.600, the cyan toner is apt to show a strong yellow color. WhenA_(C420) is less than 0.250, the cyan toner is apt to show a strong redcolor. Accordingly, the range of A_(C420) is more preferably 0.300 to0.550, or particularly preferably 0.380 to 0.550.

The cyan toner of the present invention has a ratio (A_(C710)/A_(C670))of an absorbance (A_(C710)) at a wavelength of 710 nm to A_(C670) ofpreferably 1.00 to 1.30 in the reflectance spectrophotometry. Anincrease in addition amount of the colorant in the toner is apt to causeA_(C710)/A_(C670) to have a small value. However, when A_(C710)/A_(C670)falls within the above range, color development efficiency uponformation of a secondary color becomes additionally good. WhenA_(C710)/A_(C670) is less than 1.00, the lightness of a secondary colorimage is apt to reduce. When A_(C710)/A_(C670) exceeds 1.30, the chromaof a secondary color may reduce. The range of A_(C710)/A_(C670)described above is more preferably 1.00 to 1.20, or particularlypreferably 1.01 to 1.08.

The cyan toner of the present invention has a value (L*_(C)) for L* ofpreferably 35.0 to 60.0 in the reflectance spectrophotometry. With suchconstitution, the chroma of an image is improved, the representablecolor space of the image expands, and the quality of the image becomesadditionally good. When L*_(C) is less than 35.0, a representable colorspace may become small if a full-color image is formed by combining thetoner with any other toner. When L*_(C) exceeds 60.0, a sufficient imagedensity is hardly obtained. When a toner amount on paper is increased,an image resolution is apt to reduce, and the unevenness of an imagebecomes large, so the appearance of the image is apt to reduce.Accordingly, the range of L*_(C) described above is more preferably 40.0to 56.0, or particularly preferably 42.0 to 50.0.

The cyan toner of the present invention has a value (c*_(C)) for c*based on the CIELAB color coordinate system of preferably 55.0 to 75.0in the reflectance spectrophotometry. With such constitution, therepresentable color space of an image expands, and a toner amount onpaper can be additionally reduced. When c*_(C) is less than 55.0, asufficient image density is hardly obtained. When a toner amount onpaper is increased, an image resolution is apt to reduce, and theunevenness of an image becomes large, so the appearance of the image isapt to reduce. When c*_(C) exceeds 75.0, if a full-color image is formedby combining the toner with any other toner, a color balance is apt tocollapse. Accordingly, c*_(C) described above is more preferably 60.0 to75.0, or particularly preferably 63.0 to 70.0.

A cyan toner of the present invention has a viscosity (η_(C105)) at 105°C. of 500 to 100,000 Pa·s, a viscosity (η_(C120)) at 120° C. of 100 to20,000 Pa·s, and a ratio (η_(C105)/η_(C120)) of η_(C105) to η_(C120) ofpreferably 3.0 to 50.0.

In the present invention, η_(C105), η_(C120), and η_(C105)/η_(C120) showthe melt properties of the toner. The smaller η^(C105) or η_(C120), themore apt to melt and deform at a low temperature the toner is. Asη_(C105)/η_(C120) becomes closer to 1.0, a change in melt viscosity ofthe toner with temperature becomes smaller.

Since the cyan toner of the present invention has higher colordevelopment property than that of an ordinary toner, even when an imageis formed for one kind of image data with a smaller toner amount thanthat in the case where the ordinary toner is used, an image density andan image color gamut each of which is comparable to a conventional onecan be achieved. However, when one attempts to reduce a tonerconsumption by reducing the thickness of a toner layer of which theimage is formed, the toner penetrates into paper, and a fiber of thepaper is apt to be remarkable in an image portion unless the tonerretains some degree of viscosity in a fixing process. Alternatively, theappearance of the image is apt to reduce owing to a phenomenon such as areduction in chroma of the image. When the image is formed while a toneramount on the paper is reduced, the amount of a binder resin of whichthe image is constituted also reduces, so cold offset and hot offset areparticularly apt to occur. In view of the foregoing, the toner of thepresent invention, which is excellent in low-temperature fixability tosome extent, preferably retains an appropriate viscosity even at hightemperatures.

According to the present invention, when an image is formed while atoner amount on paper is reduced, the image is susceptible to moisturein the paper in the fixing step. Accordingly, in the present invention,a change in melt viscosity of the toner at 105 to 120° C. astemperatures each exceeding the boiling point of water is preferablycontrolled. In the case where η_(C105) described above exceeds 100,000Pa·s, or η_(C120) exceeds 20,000 Pa·s, when the toner is used while thetoner amount on the paper is reduced, cold offset is apt to occur. Inaddition, the color development property of the toner is notsufficiently exerted, and the representable color gamut of the imagereduces in some cases. In the case where η_(C105) is less than 500 Pa·s,or η_(C120) is less than 100 Pa·s, when the toner is used while thetoner amount on the paper is reduced, hot offset is apt to occur. Inaddition, the toner penetrates into the paper, the color gamut of theimage reduces, and a fiber of the paper becomes remarkable in an imageportion, with the result that the appearance of the image is apt toreduce.

In addition, in the case where η_(C105)/η_(C120) described above exceeds50.0, the toner penetrates into the paper, and the chroma of the imagereduces, or a fiber of the paper becomes remarkable in the imageportion, with the result that the appearance of the image is apt toreduce. In the case of duplex printing, the following problem may arise:an image on a front surface stands on a back surface. Further, hotoffset is apt to occur. In the case where η_(C105)/η_(C120) is less than3.0, cold offset is apt to occur, or the toner does not undergosufficient melting and deformation in the fixing step, so the colordevelopment property of the toner is not sufficiently exerted, and therepresentable color gamut of the image reduces in some cases. Further,the front end portion and rear end portion of the paper are apt todiffer from each other in image gloss or image color gamut with respectto the travelling direction of the paper in the fixing step, so theappearance of the image is apt to reduce.

Accordingly, the value for η_(C105) described above is more preferably500 to 50,000 Pa·s, or particular preferably 1,000 to 30,000 Pa·s.Similarly, the value for η_(C120) described above is more preferably 100to 10,000 Pa·s, or particularly preferably 400 to 5,000 Pa·s. Inaddition, η_(C105)/η_(C120) described above is more preferably 3.0 to25.0, or particularly preferably 5.0 to 20.0.

The cyan toner of the present invention has the highest endothermic peakwith a differential scanning calorimeter (DSC) at preferably 60 to 140°C. The endothermic peak derives from the melting point of a wax in thetoner; the melting and deformation of the toner in the fixing step aresignificantly promoted when the toner present in an image portion isheated to a temperature equal to or higher than the melting point of thewax. Accordingly, when a toner amount on paper is reduced, theendothermic peak is susceptible to the melting behavior of the wax inthe fixing step. In addition, in the case where a fixing process inwhich no oil application mechanism is present or only a trace amount ofoil is applied is employed in the fixing step, when an image is formedwhile a toner amount on paper is reduced, the amount of the tonerpresent on the paper is small, so the amount of the wax in a toner layerof which the image is constituted also reduced. Accordingly, when animage is formed for one kind of image data with a smaller toner amountthan that in the case where the ordinary toner is used, cold offset andhot offset are particularly apt to occur. When the temperature of thehighest endothermic peak is lower than 60° C., upon melting of the waxin the fixing step, the wax is apt to dissolve in the binder resin in alarge amount, and the melt viscosity of the toner is apt to reduce. As aresult, the value for η_(C105) or η_(C120) described above is apt todecrease, and the value for η_(C105)/η_(C120) described above is apt toincrease. In addition, upon melting of the wax in the fixing step, partof the wax dissolves in the binder resin, and the releasing performanceof the toner is apt to reduce. Accordingly, when the toner is used whileits consumption is reduced, hot offset is remarkably apt to occur. Onthe other hand, when the temperature of the highest endothermic peakexceeds 140° C., upon melting of the wax in the fixing step, the amountin which the wax dissolves in the binder resin is remarkably small, sothe plasticizing effect of the wax is hardly obtained. As a result, thevalue for η_(C105) or η_(C120) described above is apt to increase, andthe value for η_(C105)/η_(C120) described above is apt to decrease. Inaddition, a wax having the highest endothermic peak at a temperature inexcess of 140° C. has large crystallinity, so, when a toner amount onpaper is reduced, a wax crystal to be mixed in a fixed image has asignificant influence on the representable color gamut of an image, andthe color gamut is apt to reduce. Accordingly, the highest endothermicpeak is placed at more preferably 65° C. to 95° C., or still morepreferably 60° C. to 90° C.

By the same reason as that described above, the half width of thehighest endothermic peak possessed by the cyan toner of the presentinvention is preferably 0.5 to 20.0° C. In addition, in the case where atoner amount on paper is reduced, when the half width exceeds 20.0° C.,gloss non-uniformity or density non-uniformity is apt to arise in animage at each of the former half portion and latter half portion of thedirection in which the paper is passed. When the half width is less than0.5° C., offset is apt to occur at the latter half portion of thedirection in which the paper is passed. Accordingly, the half width ismore preferably 1.0 to 15.0° C., or particularly preferably 2.0 to 10.0°C.

The cyan toner of the present invention can use a suitable colorant in asuitable addition amount so as to exert the reflection spectralcharacteristics. The addition amount of the colorant is preferably 8 to18 parts by mass with respect to 100 parts by mass of the binder resin.A coloring material is preferably incorporated in as small an amount aspossible into the toner in order that a running cost may be reduced.However, when the content of the colorant is less than 8 parts by mass,sufficient color development property may not be obtained. In addition,when the content of the colorant exceeds 18 parts by mass, therepresentable color space of an image may reduce.

In the cyan toner of the present invention, a relationship between anacid value (A_(C)1) of a first soluble component out of solvent-solublecomponents extracted from the cyan toner with isopropanol frominitiation of the extraction to 20 mass % with reference to a total massof the soluble components and an acid value (A_(M)2) of a second solublecomponent out of the solvent-soluble components in excess of 20 mass %to 100 mass % with reference to the total mass preferably satisfies thefollowing expression 1A _(C)1>A _(C)2  (Ex. 1).

In a developing device, the toner is apt to be damaged by a mechanicalstress from a toner carrying member, an electrostatic image bearingmember, or any other member. Part of the toner chips, or is broken, toproduce a fine powder in some cases. The fine powder adheres to any oneof the members to change the charging performance of the toner or tocontaminate paper directly, and image appearance is reduced in somecases. In particular, in the case of a cyan toner having high coloringpower like the toner of the present invention, the charging performanceof the toner is susceptible to a colorant even when a trace amount of afine powder adheres, and the extent to which paper is contaminated whena fine powder adheres to the paper is apt to be large. Accordingly, thecharging characteristic of the toner of the present invention ispreferably controlled more precisely than in the case of a conventionaltoner. In the present invention, the following procedure is preferablyadopted: the surface layer of a toner particle is provided with a resinlayer having a higher acid value than that of the inside of the tonerparticle, and the exposure of the colorant in the toner particle to atoner surface is suppressed. In addition, when the surface layer of thetoner particle is provided with the resin layer having a high acidvalue, a polar group derived from the acid value is considered to act asa charging auxiliary agent, so a charging failure hardly occurs. Whenthe acid value (A_(C)1) of a first soluble component out ofsolvent-soluble components extracted from the cyan toner of the presentinvention with isopropanol from the initiation of the extraction to 20mass % with reference to the total mass of the soluble components, thatis, a component the main component of which is considered to be a resinof which a toner surface layer is formed and the acid value (A_(C)2) ofa second soluble component out of the solvent-soluble components inexcess of 20 mass % to 100 mass % with reference to the total mass, thatis, a component the main component of which is considered to be a resinof which a toner core portion is formed satisfy the expression 1, thefirst component forms the toner surface layer, whereby the exposure ofthe colorant to a toner surface is suppressed, and the chargingperformance of the toner becomes additionally good by virtue of thepresence of a large amount of a resin having a large acid value on thetoner surface.

A_(C)1 described above is preferably 3.0 to 50.0 mgKOH/g. When A_(C)1 isless than 3.0 mgKOH/g, an improving effect on the charging performanceof the toner by virtue of the presence of a component having a high acidvalue on the surface of the toner is apt to be small. When A_(C)1exceeds 50.0 mgKOH/g, a polar group derived from the acid value of thecomponent and a polar group in the colorant interact with each other, sothe color development property of the toner reduces in some cases.Accordingly, A_(C)1 described above is particularly preferably 5.0 to30.0 mgKOH/g. In addition, by the same reason as that described above, adifference (A_(C)1-A_(C)2) between A_(C)1 and A_(C)2 is preferably 0.5to 30.0 mgKOH/g, or more preferably 2.0 to 20.0 mgKOH/g.

A_(C)1 and A_(C)2 described above can be controlled by using two or morekinds of resins having different acid values and controlling the statesof presence of the resins in the toner. To be specific, for example, anyone of the following methods can be employed: (1) a method involvingadding, to the toner, a charge control resin having a large acid valuethan that of the binder resin out of the charge control resins eachhaving a sulfonic group or a carboxylic group, (2) a method involvingforming, near the surface of the toner, a coat layer having a resinhaving a larger acid value than that of the binder resin out of theresins each having a sulfonic group or a carboxylic group, and (3) amethod in which a binder resin having a sulfonic group or a carboxylicgroup and a high acid value, and a binder resin having a sulfonic groupor a carboxylic group and a low acid value are used, and the probabilitythat the binder resin having a high acid value is present is increasedby a method such as phase separation from the central portion of thetoner toward the surface of the toner.

It is preferable that: the cyan toner of the present invention contain60.0 to 97.0 mass % of a tetrahydrofuran (THF)-soluble component; andthe THF-soluble component contain 0.010 to 1.500 mass % of a sulfurelement derived from a sulfonic group. The toner of the presentinvention is more excellent in color development property than anordinary toner, and can be used in a reduced amount. The chargingcharacteristic of the toner is preferably set to be larger than that inan ordinary case in order that the amount of the toner to be used indevelopment may be reduced. However, the addition of a large amount of acharge control agent to the toner may reduce the color developmentproperty of the toner. When the THF-soluble component of the toner ofthe present invention contains a predetermined amount of a sulfonicgroup, the charging characteristic of the toner can be improved withoutany reduction in color development property of the toner. In addition,the sulfonic group easily undergoes an interaction with the binder resinor any other additive in the toner such as a hydrogen bond or an ionicbond, so the color development property of the toner can be exerted in aparticularly favorable manner. Meanwhile, the content of the THF-solublecomponent in the toner may reduce owing to the polarity of the sulfonicgroup. Further, when an image is formed while the usage of the toner isreduced as compared to an ordinary case, the offset resistance, glossuniformity, and penetration resistance of the image are apt to reduce.When the content of the THF-soluble component is less than 60.0 mass %,the color development property of the toner is apt to reduce. When thecontent of the THF-soluble component exceeds 97.0 mass %, the offsetresistance, the gloss uniformity, and the penetration resistance are aptto reduce. In addition, when the content of the sulfur element is lessthan 0.010 mass %, the extent to which the color development property ofthe toner is improved may be small. In addition, the amount of the tonerto be used in development increases, so dot reproducibility reduces insome cases. When the content of the sulfur element exceeds 1.500 mass %,an interaction between the sulfonic group and the colorant increases, sothe color development property of the toner reduces in some cases. Inaddition, the adsorptivity of the toner to a toner carrying member or anelectrostatic image bearing member becomes large, and dotreproducibility reduces in some cases. It should be noted that thecontent of the above THF-soluble component is more preferably 70.0 to95.0 mass %, still more preferably 75.0 to 95.0 mass %, or particularlypreferably 80.0 to 93.0 mass %. In addition, the content of the abovesulfur element derived from the sulfonic group is more preferably 0.010to 0.500 mass %, still more preferably 0.010 to 0.150 mass %, orparticularly preferably 0.020 to 0.100 mass %.

A magenta toner of the present invention will be described.

The magenta toner of the present invention includes at least: a binderresin; and a colorant. The magenta toner has a value (h*_(M)) for a hueangle h* based on a CIELAB color coordinate system of 330.0 to 30.0, anabsorbance (A_(M570)) at a wavelength of 570 nm of 1.550 or more, anabsorbance (A_(M620)) at a wavelength of 620 nm of 0.250 or less, and aratio (A_(M570)/A_(M450)) of A_(M570) to an absorbance (A_(M450)) at awavelength of 450 nm of 1.80 to 3.50 in reflectance spectrophotometry.

The phrase “magenta toner has h*_(M) of 330.0 to 30.0 in the reflectancespectrophotometry” as used in the present invention means that the toneris a toner having a magenta color. When h*_(M) is less than 330.0, thetoner shows a color close to a purple color. When h*_(M) exceeds 30.0,the toner shows a color close to an orange color. In addition, A_(M570),A_(M620), and A_(M570)/A_(M450) each show color development property ata specific absorption wavelength of magenta.

In the case of the magenta toner having h*_(M) within the above range,the larger A_(M570), the larger opacifying power the magenta toner has;a magenta image having a high image density can be formed with a smalltoner amount. The smaller A_(M620), the more excellent in colordevelopment property the magenta toner is; a magenta image havingadditionally large lightness can be formed. In addition,A_(M570)/A_(M450) is involved in the tinge of the toner, and, when thevalues therefor fall within the above range, a full-color imagefavorably expressing color development property even in a secondarycolor and having a good color space can be formed.

An increase in addition amount of the colorant in the magenta toner isapt to cause A_(M620) to have a large value. However, when A_(M620)exceeds 0.250, the lightness of an image reduces so that the imagebecomes obscure even if a sufficient image density is obtained. WhenA_(M570) is less than 1.550, a sufficient image density cannot beobtained, or a toner amount on paper must be increased, so effects ofthe present invention such as a reduction in unevenness of the surfaceof an image, an improvement in resolution of the image, and a reductionin toner consumption cannot be obtained. In addition, an increase inaddition amount of the colorant in the magenta toner is apt to causeA_(M570)/A_(M450) to have a small value. However, when A_(M570)/A_(M450)is less than 1.80, the magenta toner shows a strong yellow color, and anability to represent a secondary color is as follows: a color gamut neara purple color becomes small. When A_(M570)/A_(M450) is more than 3.50,the magenta toner shows a strong blue color, and the ability torepresent a secondary color is as follows: a color gamut near a redcolor becomes small.

According to the present invention, the value for A_(M570) describedabove is preferably large because a toner amount on paper can bereduced, and the effects of the present invention become large. However,the value for A_(M570) described above is preferably 2.300 or less inconsideration of a color balance when a full-color image is formed bycombining the magenta toner with any other color toner such as a cyantoner, a yellow toner, or a black toner, the color developmentefficiency of the colorant of the magenta toner, and a material cost.The range of A_(M570) described above is more preferably 1.600 to 2.200,or particularly preferably 1.800 to 2.200.

The value for A_(M620) described above is preferably small because animage excellent in color development property, and having additionallylarge lightness and additionally large chroma can be formed. However,the value for A_(M620) described above is preferably 0.050 or more inconsideration of a color balance when a full-color image is formed bycombining the magenta toner with any other color toner such as a cyantoner, a yellow toner, or a black toner, the color developmentefficiency of the colorant of the magenta toner, and a material cost.The range of A_(M620) described above is more preferably 0.050 to 0.200,still more preferably 0.100 to 0.174, or particularly preferably 0.150to 0.170.

The range of the value for A_(M570)/A_(M450) described above is morepreferably 2.00 to 3.20, or particularly preferably 2.20 to 2.70. Thisis because a color balance becomes particularly preferable, and arepresentable color space of an image becomes particularly large.

A_(M620), A_(M570) and A_(M570)/A_(M450) described above can each becontrolled depending on, for example, the kind and addition amount ofthe colorant in the toner, the state of presence of the colorant in thetoner, the state of presence of any other additive or the like, and thecolor of an additive.

A_(M450) described above is preferably 0.400 to 1.100. An increase inaddition amount of the colorant in the toner is apt to cause A_(M450) tohave a large value. When A_(M450) exceeds 1.100, the magenta toner isapt to show a strong yellow color, and an ability to represent asecondary color is as follows: a color gamut near a purple color is aptto be small. When A_(M450) is less than 0.400, the magenta toner is aptto show a strong blue color, and the ability to represent a secondarycolor is as follows: a color gamut near a red color is apt to be small.Accordingly, the range of the value for A_(M450) is more preferably0.560 to 1.000, or particularly preferably 0.700 to 0.950.

In the present invention, by the same reason as that described above,the toner of the present invention has an absorbance (A_(M490)) at awavelength of 490 nm of preferably 0.600 to 1.500. When A_(M490) is lessthan 0.600, the magenta toner is apt to show a strong blue color. WhenA_(M490) exceeds 1.500, the magenta toner is apt to show a strong yellowcolor. Accordingly, the range of A_(M490) is more preferably 0.800 to1.400, or particularly preferably 0.900 to 1.360.

The toner of the present invention has a ratio (A_(M570)/A_(M550)) ofA_(M570) to an absorbance (A_(M550)) at a wavelength of 550 nm ofpreferably 0.98 to 1.20 in the reflectance spectrophotometry. Anincrease in amount of the colorant in the toner is apt to causeA_(M570)/A_(M550) to take a small value. When A_(M570)/A_(M550) is lessthan 0.98, an image having small lightness is apt to be obtained. WhenA_(M570)/A_(M550) exceeds 1.20, an image having small chroma is apt tobe obtained. Accordingly, the range of A_(M570)/A_(M550) is morepreferably 0.98 to 1.10, or particularly preferably 0.98 to 1.06.

The magenta toner of the present invention has a value (L*_(M)) for L*of preferably 35.0 to 55.0 in the reflectance spectrophotometry. Withsuch constitution, the representable color space of the image expands,and the quality of the image becomes additionally good. When L*_(M) isless than 35.0, a representable color space may become small if afull-color image is formed by combining the toner with any other toner.When L*_(M) exceeds 55.0, a sufficient image density is hardly obtained.When a toner amount on paper is increased, an image resolution is apt toreduce, and the unevenness of an image becomes large, so the appearanceof the image is apt to reduce. Accordingly, the range of L*_(M)described above is more preferably 40.0 to 52.0, or particularlypreferably 40.0 to 49.0.

The magenta toner of the present invention has a value (c*_(M)) for c*based on the CIELAB color coordinate system of preferably 70.0 to 85.0in the reflectance spectrophotometry. With such constitution, therepresentable color space of an image expands, and a toner amount onpaper can be additionally reduced. When c*_(M) is less than 70.0, asufficient image density is hardly obtained. When a toner amount onpaper is increased, an image resolution is apt to reduce, and theunevenness of an image becomes large, so the appearance of the image isapt to reduce. When c*_(M) exceeds 85.0, if a full-color image is formedby combining the toner with any other toner, a color balance may be aptto collapse. Accordingly, c*_(M) described above is more preferably 75.0to 85.0, or particularly preferably 77.0 to 82.0.

It is preferable that the magenta toner of the present invention have aviscosity (η_(M 105)) at 105° C. of 500 to 100,000 Pa·s, a viscosity(η_(M120)) at 120° C. of 100 to 20,000 Pa·s, and a ratio(η_(M105)/η_(M120)) of η_(M105) to η_(M120) of 3.0 to 50.0.

In the present invention, η_(M105), η_(M120) and η_(M105)/η_(M120) showthe melt properties of the toner. The smaller η_(M105) or η_(M120), themore apt to melt and deform at a low temperature the toner is. Asη_(M105)/η_(M120) becomes closer to 1.0, a change in melt viscosity ofthe toner with temperature becomes smaller.

Since the magenta toner of the present invention has higher colordevelopment property than that of an ordinary toner, even when an imageis formed for one kind of image data with a smaller toner amount thanthat in the case where the ordinary toner is used, an image density andan image color gamut each of which is comparable to a conventional onecan be achieved. However, when one attempts to reduce a tonerconsumption by reducing the thickness of a toner layer of which theimage is formed, the toner penetrates into paper, and a fiber of thepaper is apt to be remarkable in an image portion unless the tonerretains some degree of viscosity in a fixing process. Alternatively, theappearance of the image is apt to reduce owing to a phenomenon such as areduction in chroma of the image. When the image is formed while a toneramount on the paper is reduced, the amount of a binder resin of whichthe image is constituted also reduces, so cold offset and hot offset areparticularly apt to occur. In view of the foregoing, the toner of thepresent invention, which is excellent in low-temperature fixability tosome extent, preferably retains an appropriate viscosity even at hightemperatures.

According to the present invention, when an image is formed while atoner amount on paper is reduced, the image is susceptible to moisturein the paper in the fixing step. Accordingly, in the present invention,a change in melt viscosity of the toner at 105 to 120° C. astemperatures each exceeding the boiling point of water is preferablycontrolled. In the case where η_(M105) described above exceeds 100,000Pa·s, or η_(M120) exceeds 20,000 Pa·s, when the toner is used while thetoner amount on the paper is reduced, cold offset is apt to occur. Inaddition, the color development property of the toner is notsufficiently exerted, and the representable color gamut of the imagereduces in some cases. In the case where η_(M105) is less than 500 Pa·s,or η_(M120) is less than 100 Pa·s, when the toner is used while thetoner amount on the paper is reduced, hot offset is apt to occur. Inaddition, the toner penetrates into the paper, the color gamut of theimage reduces, and a fiber of the paper becomes remarkable in an imageportion, with the result that the appearance of the image is apt toreduce.

In addition, in the case where η_(M105)/η_(M120) described above exceeds50.0, the toner penetrates into the paper, and the chroma of the imagereduces, or a fiber of the paper becomes remarkable in the imageportion, with the result that the appearance of the image is apt toreduce. In the case of duplex printing, the following problem may arise:an image on a front surface stands on a back surface. Further, hotoffset is apt to occur. In the case where η_(M105)/η_(M120) is less than3.0, cold offset is apt to occur, or the toner does not undergosufficient melting and deformation in the fixing step, so the colordevelopment property of the toner is not sufficiently exerted, and therepresentable color gamut of the image reduces in some cases. Further,the front end portion and rear end portion of the paper are apt todiffer from each other in image gloss or image color gamut with respectto the travelling direction of the paper in the fixing step, so theappearance of the image is apt to reduce.

Accordingly, the value for η_(M105) described above is more preferably500 to 50,000 Pa·s, or particular preferably 1,000 to 30,000 Pas.Similarly, the value for η_(M120) described above is more preferably 100to 10,000 Pa·s, or particularly preferably 400 to 5,000 Pas. Inaddition, η_(M105)/η_(M120) described above is more preferably 3.0 to25.0, or particularly preferably 5.0 to 20.0.

The magenta toner of the present invention has the highest endothermicpeak with a differential scanning calorimeter (DSC) at preferably 60 to140° C. The endothermic peak derives from the melting point of a wax inthe toner; the melting and deformation of the toner in the fixing stepare significantly promoted when the toner present in an image portion isheated to a temperature equal to or higher than the melting point of thewax. Accordingly, when a toner amount on paper is reduced, theendothermic peak is susceptible to the melting behavior of the wax inthe fixing step. In addition, in the case where a fixing process inwhich no oil application mechanism is present or only a trace amount ofoil is applied is employed in the fixing step, when an image is formedwhile a toner amount on paper is reduced, the amount of the tonerpresent on the paper is small, so the amount of the wax in a toner layerof which the image is constituted also reduced. Accordingly, when animage is formed for one kind of image data with a smaller toner amountthan that in the case where the ordinary toner is used, cold offset andhot offset are particularly apt to occur. When the temperature of thehighest endothermic peak is lower than 60° C., upon melting of the waxin the fixing step, the wax is apt to dissolve in the binder resin in alarge amount, and the melt viscosity of the toner is apt to reduce. As aresult, the value for η_(M105) or η_(M120) described above is apt todecrease, and the value for η_(M105)/η_(M120) described above is apt toincrease. In addition, upon melting of the wax in the fixing step, partof the wax dissolves in the binder resin, and the releasing performanceof the toner is apt to reduce. Accordingly, when the toner is used whileits consumption is reduced, hot offset is remarkably apt to occur. Onthe other hand, when the temperature of the highest endothermic peakexceeds 140° C., upon melting of the wax in the fixing step, the amountin which the wax dissolves in the binder resin is remarkably small, sothe plasticizing effect of the wax is hardly obtained. As a result, thevalue for η_(M105) or η_(M120) described above is apt to increase, andthe value for η_(M105)/η_(M120) described above is apt to decrease. Inaddition, a wax having the highest endothermic peak at a temperature inexcess of 140° C. has large crystallinity, so, when a toner amount onpaper is reduced, a wax crystal to be mixed in a fixed image has asignificant influence on the representable color gamut of an image, andthe color gamut is apt to reduce. Accordingly, the highest endothermicpeak is placed at more preferably 60° C. to 95° C., or still morepreferably 65° C. to 90° C.

By the same reason as that described above, the half width of thehighest endothermic peak possessed by the magenta toner of the presentinvention is preferably 0.5 to 20.0° C. In addition, in the case where atoner amount on paper is reduced, when the half width exceeds 20.0° C.,gloss non-uniformity or density non-uniformity is apt to arise in animage at each of the former half portion and latter half portion of thedirection in which the paper is passed. When the half width is less than0.5° C., offset is apt to occur at the latter half portion of thedirection in which the paper is passed. Accordingly, the half width ismore preferably 1.0 to 15.0° C., or particularly preferably 2.0 to 10.0°C.

The magenta toner of the present invention can use a suitable colorantin a suitable addition amount so as to exert the reflection spectralcharacteristics. The addition amount of the colorant is preferably 8 to18 parts by mass with respect to 100 parts by mass of the binder resin.A coloring material is preferably incorporated in as small an amount aspossible into the toner in order that a running cost may be reduced.However, when the content of the colorant is less than 8 parts by mass,sufficient color development property may not be obtained. In addition,when the content of the colorant exceeds 18 parts by mass, therepresentable color space of an image may reduce.

In a magenta toner of the present invention, it is preferable that arelationship between an acid value (A_(M)1) of a first soluble componentout of solvent-soluble components extracted from the magenta toner withisopropanol from initiation of the extraction to 20 mass % withreference to a total mass of the soluble components and an acid value(A_(M)2) of a second soluble component out of the solvent-solublecomponents in excess of 20 mass % to 100 mass % with reference to thetotal mass satisfy the following expression 3A _(M)1>A _(M)2  (Ex. 3).

In a developing device, the toner is apt to be damaged by a mechanicalstress from a toner carrying member, an electrostatic image bearingmember, or any other member. Part of the toner chips, or is broken, toproduce a fine powder in some cases. The fine powder adheres to any oneof the members to change the charging performance of the toner or tocontaminate paper directly, and image appearance is reduced in somecases. In particular, in the case of a magenta toner having highcoloring power like the toner of the present invention, the chargingperformance of the toner is susceptible to a colorant even when a traceamount of a fine powder adheres, and the extent to which paper iscontaminated when a fine powder adheres to the paper is apt to be large.Accordingly, the charging characteristic of the toner of the presentinvention is preferably controlled more precisely than in the case of aconventional toner. In the present invention, the following procedure ispreferably adopted: the surface layer of a toner particle is providedwith a resin layer having a higher acid value than that of the inside ofthe toner particle, and the exposure of the colorant in the tonerparticle to a toner surface is suppressed. In addition, when the surfacelayer of the toner particle is provided with the resin layer having ahigh acid value, a polar group derived from the acid value is consideredto act as a charging auxiliary agent, so a charging failure hardlyoccurs. When the acid value (A_(M)1) of a first soluble component out ofsolvent-soluble components extracted from the magenta toner of thepresent invention with isopropanol from the initiation of the extractionto 20 mass % with reference to the total mass of the soluble components,that is, a component the main component of which is considered to be aresin of which a toner surface layer is formed and the acid value(A_(M)2) of a second soluble component out of the solvent-solublecomponents in excess of 20 mass % to 100 mass % with reference to thetotal mass, that is, a component the main component of which isconsidered to be a resin of which a toner core portion is formed satisfythe expression 3, the first component forms the toner surface layer,whereby the exposure of the colorant to a toner surface is suppressed,and the charging performance of the toner becomes additionally good byvirtue of the presence of a large amount of a resin having a large acidvalue on the toner surface.

A_(M)1 described above is preferably 3.0 to 50.0 mgKOH/g. When A_(M)1 isless than 3.0 mgKOH/g, an improving effect on the charging performanceof the toner by virtue of the presence of a component having a high acidvalue on the surface of the toner is apt to be small. When A_(M)1exceeds 50.0 mgKOH/g, a polar group derived from the acid value of thecomponent and a polar group in the colorant interact with each other, sothe color development property of the toner reduces in some cases.Accordingly, A_(M)1 described above is particularly preferably 5.0 to30.0 mgKOH/g. In addition, by the same reason as that described above, adifference (A_(M)1-A_(M)2) between A_(M)1 and A_(M)2 is preferably 0.5to 30.0 mgKOH/g, or more preferably 2.0 to 20.0 mgKOH/g.

A_(M)1 and A_(M)2 described above can be controlled by using two or morekinds of resins having different acid values and controlling the statesof presence of the resins in the toner. To be specific, for example, anyone of the following methods can be employed: (1) a method involvingadding, to the toner, a charge control resin having a large acid valuethan that of the binder resin out of the charge control resins eachhaving a sulfonic group or a carboxylic group, (2) a method involvingforming, near the surface of the toner, a coat layer having a resinhaving a larger acid value than that of the binder resin out of theresins each having a sulfonic group or a carboxylic group, and (3) amethod in which a binder resin having a sulfonic group or a carboxylicgroup and a high acid value, and a binder resin having a sulfonic groupor a carboxylic group and a low acid value are used, and the probabilitythat the binder resin having a high acid value is present is increasedby a method such as phase separation from the central portion of thetoner toward the surface of the toner.

It is preferable that: the magenta toner of the present inventioncontain 60.0 to 97.0 mass % of a tetrahydrofuran (THF)-solublecomponent; and the THF-soluble component contain 0.010 to 1.500 mass %of a sulfur element derived from a sulfonic group. The toner of thepresent invention is more excellent in color development property thanan ordinary toner, and can be used in a reduced amount. The chargingcharacteristic of the toner is preferably set to be larger than that inan ordinary case in order that the amount of the toner to be used indevelopment may be reduced. However, the addition of a large amount of acharge control agent to the toner may reduce the color developmentproperty of the toner. When the THF-soluble component of the toner ofthe present invention contains a predetermined amount of a sulfonicgroup, the charging characteristic of the toner can be improved withoutany reduction in color development property of the toner. In addition,the sulfonic group easily undergoes an interaction with the binder resinor any other additive in the toner such as a hydrogen bond or an ionicbond, so the color development property of the toner can be exerted in aparticularly favorable manner. Meanwhile, the content of the THF-solublecomponent in the toner may reduce owing to the polarity of the sulfonicgroup. Further, when an image is formed while the usage of the toner isreduced as compared to an ordinary case, the offset resistance, glossuniformity, and penetration resistance of the image are apt to reduce.When the content of the THF-soluble component is less than 60.0 mass %,the color development property of the toner is apt to reduce. When thecontent of the THF-soluble component exceeds 97.0 mass %, the offsetresistance, the gloss uniformity, and the penetration resistance are aptto reduce. In addition, when the content of the sulfur element is lessthan 0.010 mass %, the extent to which the color development property ofthe toner is improved may be small. In addition, the amount of the tonerto be used in development increases, so dot reproducibility reduces insome cases. When the content of the sulfur element exceeds 1.500 mass %,an interaction between the sulfonic group and the colorant increases, sothe color development property of the toner reduces in some cases. Inaddition, the adsorptivity of the toner to a toner carrying member or anelectrostatic image bearing member becomes large, and dotreproducibility reduces in some cases. It should be noted that thecontent of the above THF-soluble component is more preferably 70.0 to95.0 mass %, still more preferably 75.0 to 95.0 mass %, or particularlypreferably 80.0 to 93.0 mass %. In addition, the content of the abovesulfur element derived from the sulfonic group is more preferably 0.010to 0.500 mass %, still more preferably 0.010 to 0.150 mass %, orparticularly preferably 0.020 to 0.100 mass %.

A yellow toner of the present invention will be described.

The yellow toner of the present invention includes at least: a binderresin; and a colorant. The yellow toner has a value (h*_(Y)) for a hueangle h* based on a CIELAB color coordinate system of 75.0 to 120.0, anabsorbance (A_(Y450)) at a wavelength of 450 nm of 1.600 or less, anabsorbance (A_(Y470)) at a wavelength of 470 nm of 1.460 or more, and anabsorbance (A_(Y510)) at a wavelength of 510 nm of 0.500 or less inreflectance spectrophotometry.

The phrase “yellow toner has h*_(Y) of 75.0 to 120.0 in the reflectancespectrophotometry” as used in the present invention means that the toneris a toner having a yellow color. When h*_(Y) is less than 75.0, thetoner shows a color close to an orange color. When h*_(Y) exceeds 120.0,the toner shows a color close to a greenish yellow color. In addition,A_(Y450), A_(Y470), and A_(Y510) each show color development property ata specific absorption wavelength of yellow.

In the case of the yellow toner having h*_(Y) within the above range,the larger A_(Y450) or A_(Y470), the larger opacifying power the yellowtoner has; a yellow image having a high image density can be formed witha small toner amount. In addition, the smaller A_(Y510), the moreexcellent in color development property the yellow toner is; afull-color image favorably expressing color development property even ina secondary color and having a good color space can be formed.

An increase in addition amount of the colorant in the yellow toner isapt to cause A_(Y510) to have a large value. However, when A_(Y510)exceeds 0.500, the lightness of an image reduces so that the imagebecomes obscure even if a sufficient image density is obtained.Accordingly, when a full-color image is formed, a representable colorspace becomes small. On the other hand, A_(Y450) is less than 1.600, orwhen A_(Y470) is less than 1.460, a sufficient image density cannot beobtained, or a toner amount on paper must be increased, so effects ofthe present invention such as a reduction in unevenness of the surfaceof an image, an improvement in resolution of the image, and a reductionin toner consumption cannot be obtained.

According to the present invention, the value for A_(Y450) describedabove is preferably large because a toner amount on paper can bereduced, and the effects of the present invention become large. However,the value for A_(Y450) described above is preferably 2.300 or less inconsideration of a color balance when a full-color image is formed bycombining the yellow toner with any other color toner such as a cyantoner, a magenta toner, or a black toner, the color developmentefficiency of the colorant of the yellow toner, and a material cost. Therange of A_(Y450) described above is more preferably 1.650 to 2.200,still more preferably 1.700 to 2.200, or particularly preferably 1.780to 2.100.

Similarly, the value for A_(Y470) described above is preferably 2.200 orless. The range of A_(Y470) described above is more preferably 1.500 to2.100, still more preferably 1.650 to 2.000, or particularly preferably1.700 to 1.980.

The value for A_(Y510) described above is preferably small because animage excellent in color development property, and having additionallylarge lightness and additionally large chroma can be formed. However,the value for A_(Y510) described above is preferably 0.020 or more inconsideration of a color balance when a full-color image is formed bycombining the yellow toner with any other color toner such as a cyantoner, a magenta toner, or a black toner, the color developmentefficiency of the colorant of the yellow toner, and a material cost. Therange of A_(Y510) described above is more preferably 0.050 to 0.350, orparticularly preferably 0.150 to 0.320.

The yellow toner of the present invention has a ratio(A_(Y470)/A_(Y490)) of an absorbance (A_(Y490)) at a wavelength of 490nm to A_(Y470) of preferably 1.20 to 2.10 in the reflectancespectrophotometry. An increase in addition amount of the colorant in thetoner is apt to cause A_(Y470)/A_(Y490) to have a small value. WhenA_(Y470)/A_(Y490) is less than 1.20, the yellow toner is apt to show astrong red color, and an ability to represent a secondary color is asfollows: a color gamut near a green color is apt to be small. WhenA_(Y470)/A_(Y490) exceeds 2.10, the yellow toner is apt to show a stronggreen color, and the ability to represent a secondary color is asfollows: a color gamut near a red color is apt to be small. Accordingly,the range of the value for A_(Y470)/A_(Y490) is more preferably 1.30 to1.90, still more preferably 1.30 to 1.60, or particularly preferably1.40 to 1.52.

The yellow toner of the present invention has a value (L*_(Y)) for L* ofpreferably 85.0 to 100.0 in the reflectance spectrophotometry. With suchconstitution, the representable color space of an image expands, and thequality of the image becomes additionally good. When L*_(Y) is less than85.0, the lightness of an image reduces, and a representable color spacebecomes small in some cases. When L*_(Y) exceeds 100.0, if a full-colorimage is formed by combining the toner with any other toner, a colorbalance may be apt to collapse. Accordingly, L*_(Y) described above ismore preferably 90.0 to 100.0, still more preferably 90.0 to 95.0, orparticularly preferably 91.0 to 93.0.

The yellow toner of the present invention has a value (c*_(Y)) for c*based on the CIELAB color coordinate system of preferably 95.0 to 130.0in the reflectance spectrophotometry. With such constitution, therepresentable color space of an image expands, and a toner amount onpaper can be additionally reduced. When c*_(Y) is less than 95.0, thechroma of the image is apt to reduce, and the toner amount on the papermust be increased in some cases. When c*_(Y) exceeds 130.0, if afull-color image is formed by combining the toner with any other toner,a color balance may be apt to collapse. Accordingly, c*_(Y) describedabove is more preferably 103.0 to 125.0, still more preferably 103.0 to118.0, or particularly preferably 108.0 to 118.0.

It is preferable that the cyan toner of the present invention have aviscosity (η_(Y105)) at 105° C. of 500 to 100,000 Pa·s, a viscosity(η_(Y120)) at 120° C. of 100 to 20,000 Pa·s, and a ratio(η_(Y105)/η_(Y120)) of η_(Y105) to η_(Y120) of 3.0 to 50.0.

In the present invention, η_(Y105), η_(Y120), and η_(Y105)/η_(Y120) showthe melt properties of the toner. The smaller η_(Y105) or η_(Y120), themore apt to melt and deform at a low temperature the toner is. Asη_(Y105)/η_(Y120) becomes closer to 1.0, a change in melt viscosity ofthe toner with temperature becomes smaller.

Toner is preferably excellent in low-temperature fixability in orderthat an image-forming apparatus may operate at a high speed and mayconsume reduced energy. However, when one attempts to reduce a tonerconsumption by reducing the thickness of a toner layer of which an imageis formed, toner penetrates into paper, and a fiber of the paper is aptto be remarkable in an image portion unless the toner retains somedegree of viscosity in a fixing process. Alternatively, the appearanceof the image is apt to reduce owing to a phenomenon such as a reductionin chroma of the image. In addition, when the image is formed while atoner amount on the paper is reduced, the amount of a binder resinpresent on the paper by being incorporated into the toner reduces, socold offset and hot offset are particularly apt to occur. In view of theforegoing, the toner of the present invention, which is excellent inlow-temperature fixability to some extent, preferably retains anappropriate viscosity and has suitable melt properties even at hightemperatures.

According to the present invention, when an image is formed while atoner amount on paper is reduced, the image is susceptible to moisturein the paper in the fixing step. Accordingly, in the present invention,a change in melt viscosity of the toner at 105 to 120° C. astemperatures each exceeding the boiling point of water is preferablycontrolled. In the case where η_(Y105) described above exceeds 100,000Pa·s, or η_(Y120) exceeds 20,000 Pa·s, when the toner is used while thetoner amount on the paper is reduced, cold offset is apt to occur. Inaddition, the color development property of the toner is notsufficiently exerted, and the representable color gamut of the imagereduces in some cases. In the case where η_(Y105) is less than 500 Pa·s,or η_(Y120) is less than 100 Pa·s, when the toner is used while thetoner amount on the paper is reduced, hot offset is apt to occur. Inaddition, the toner penetrates into the paper, the color gamut of theimage reduces, and a fiber of the paper becomes remarkable in an imageportion, with the result that the appearance of the image is apt toreduce.

In addition, in the case where η_(Y105)/η_(Y120) exceeds 50.0, the tonerpenetrates into the paper, and the chroma of the image reduces, or afiber of the paper becomes remarkable in the image portion, with theresult that the appearance of the image is apt to reduce. In the case ofduplex printing, the following problem may arise: an image on a frontsurface stands on a back surface. Further, hot offset is apt to occur.In the case where η_(Y105)/η_(Y120) is less than 3.0, cold offset is aptto occur, or the toner does not undergo sufficient melting anddeformation in the fixing step, so the color development property of thetoner is not sufficiently exerted, and the representable color gamut ofthe image reduces in some cases. Further, the front end portion and rearend portion of the paper are apt to differ from each other in imagegloss or image color gamut with respect to the travelling direction ofthe paper in the fixing step, so the appearance of the image is apt toreduce.

Accordingly, the value for η_(Y105) described above is more preferably500 to 50,000 Pa·s, or particular preferably 1,000 to 30,000 Pas.Similarly, the value for η_(Y120) described above is more preferably 100to 10,000 Pa·s, or particularly preferably 100 to 5,000 Pas. Inaddition, η_(Y105)/η_(Y120) described above is more preferably 3.0 to25.0, or particularly preferably 5.0 to 20.0.

Further, the yellow toner of the present invention has the highestendothermic peak with a differential scanning calorimeter (DSC) atpreferably 60 to 140° C. The endothermic peak derives from the meltingpoint of a wax in the toner; the melting and deformation of the toner inthe fixing step are significantly promoted when the toner present in animage portion is heated to a temperature equal to or higher than themelting point of the wax. Accordingly, when a toner amount on paper isreduced, the endothermic peak is susceptible to the melting behavior ofthe wax in the fixing step. In addition, in the case where a fixingprocess in which no oil application mechanism is present or only a traceamount of oil is applied is employed in the fixing step, when an imageis formed while a toner amount on paper is reduced, the amount of thetoner present on the paper is small, so the amount of the wax in a tonerlayer of which the image is constituted also reduced because the wax iscontained in the toner. Accordingly, when an image is formed for onekind of image data with a smaller toner amount than that in the casewhere the ordinary toner is used, cold offset and hot offset areparticularly apt to occur. When the temperature of the highestendothermic peak is lower than 60° C., upon melting of the wax in thefixing step, the wax is apt to dissolve in the binder resin in a largeamount, and the melt viscosity of the toner is apt to reduce. As aresult, the value for η_(Y105) or η_(Y120) described above is apt todecrease, and the value for η_(Y105)/η_(Y120) described above is apt toincrease, so the toner penetrates into the paper, the color gamut of theimage reduces, and a fiber of the paper becomes remarkable in an imageportion, with the result that the appearance of the image is apt toreduce. Further, upon melting of the wax in the fixing step, part of thewax dissolves in the binder resin, and the releasing performance of thetoner is apt to reduce. Accordingly, when the toner is used while itsconsumption is reduced, hot offset is remarkably apt to occur. On theother hand, when the temperature of the highest endothermic peak exceeds140° C., upon melting of the wax in the fixing step, the amount in whichthe wax dissolves in the binder resin is remarkably small, so theplasticizing effect of the wax is hardly obtained. As a result, thecolor gamut of the image to be expressed is apt to reduce becausefixability of toner degrades, and toner does not melt and deformsufficiently in the fixing process, whereby coloring properties of thetoner does not express sufficiently. In addition, a wax having thehighest endothermic peak at a temperature in excess of 140° C. has largecrystallinity, so, when a toner amount on paper is reduced, a waxcrystal to be mixed in a fixed image has a significant influence on therepresentable color gamut of an image, and the color gamut is apt toreduce. Accordingly, the highest endothermic peak is placed at morepreferably 60° C. to 95° C., or still more preferably 65° C. to 85° C.

By the same reason as that described above, the half width of thehighest endothermic peak possessed by the yellow toner of the presentinvention is preferably 0.5 to 20.0° C. In addition, in the case where atoner amount on paper is reduced, when the half width exceeds 20.0° C.,gloss non-uniformity or density non-uniformity is apt to arise in animage at each of the former half portion and latter half portion of thedirection in which the paper is passed. When the half width is less than0.5° C., offset is apt to occur. Accordingly, the half width is morepreferably 1.0 to 15.0° C., or particularly preferably 2.0 to 10.0° C.

The yellow toner of the present invention preferably contains thecolorant of 8 to 18 parts by mass with respect to 100 parts by mass ofthe binder resin. A coloring material is preferably incorporated in assmall an amount as possible into the toner in order that a running costmay be reduced. However, when the content of the colorant is less than 8parts by mass, sufficient color development property may not beobtained. In addition, when the content of the colorant exceeds 18 partsby mass, the representable color space of an image may reduce.

In a yellow toner of the present invention, a relationship between anacid value (A_(Y)1) of a first soluble component out of solvent-solublecomponents extracted from the isopropanol from initiation of theextraction to 20 mass % with reference to a total mass of the solublecomponents and an acid value (A_(Y)2) of a second soluble component outof the solvent-soluble components in excess of 20 mass % to 100 mass %with reference to the total mass preferably satisfies the followingexpression 5A _(Y)1>A _(Y)2  (Ex. 5).

In a developing device, the toner is apt to be damaged by a mechanicalstress from a toner carrying member, an electrostatic image bearingmember, or any other member. Part of the toner chips, or is broken, toproduce a fine powder in some cases. The fine powder adheres to any oneof the members to change the charging performance of the toner or tocontaminate paper directly, and image appearance is reduced in somecases. In particular, in the case of a yellow toner having high coloringpower like the toner of the present invention, the charging performanceof the toner is susceptible to a colorant even when a trace amount of afine powder adheres, and the extent to which paper is contaminated whena fine powder adheres to the paper is apt to be large. Accordingly, thecharging characteristic of the toner of the present invention ispreferably controlled more precisely than in the case of a conventionaltoner. In the present invention, the following procedure is preferablyadopted: the surface layer of a toner particle is provided with a resinlayer having a higher acid value than that of the inside of the tonerparticle, and the exposure of the colorant in the toner particle to atoner surface is suppressed. In addition, when the surface layer of thetoner particle is provided with the resin layer having a high acidvalue, a polar group derived from the acid value is considered to act asa charging auxiliary agent, so a charging failure hardly occurs. Whenthe acid value (A_(Y)1) of a first soluble component out ofsolvent-soluble components extracted from isopropanol from theinitiation of the extraction to 20 mass % with reference to the totalmass of the soluble components, that is, a component the main componentof which is considered to be a resin of which a toner surface layer isformed and the acid value (A_(Y)2) of a second soluble component out ofthe solvent-soluble components in excess of 20 mass % to 100 mass % withreference to the total mass, that is, a component the main component ofwhich is considered to be a resin of which a toner core portion isformed satisfy the expression 5, the first component forms the tonersurface layer, whereby the exposure of the colorant to a toner surfaceis suppressed, and the charging performance of the toner becomesadditionally good by virtue of the presence of a large amount of a resinhaving a large acid value on the toner surface.

A_(Y)1 described above is preferably 3.0 to 50.0 mgKOH/g. When A_(Y)1 isless than 3.0 mgKOH/g, an improving effect on the charging performanceof the toner by virtue of the presence of a component having a high acidvalue on the surface of the toner is apt to be small. When A_(Y)1exceeds 50.0 mgKOH/g, a polar group derived from the acid value of thecomponent and a polar group in the colorant interact with each other, sothe color development property of the toner reduces in some cases.Accordingly, A_(Y)1 described above is particularly preferably 5.0 to30.0 mgKOH/g. In addition, by the same reason as that described above, adifference (A_(Y)1-A_(Y)2) between A_(Y)1 and A_(Y)2 is preferably 0.5to 30.0 mgKOH/g, or more preferably 2.0 to 20.0 mgKOH/g.

A_(Y)1 and A_(Y)2 described above can be controlled by using two or morekinds of resins having different acid values and controlling the statesof presence of the resins in the toner. To be specific, for example, anyone of the following methods can be employed: (1) a method involvingadding, to the toner, a charge control resin having a large acid valuethan that of the binder resin out of the charge control resins eachhaving a sulfonic group or a carboxylic group, (2) a method involvingforming, near the surface of the toner, a coat layer having a resinhaving a larger acid value than that of the binder resin out of theresins each having a sulfonic group or a carboxylic group, and (3) amethod in which a binder resin having a sulfonic group or a carboxylicgroup and a high acid value, and a binder resin having a sulfonic groupor a carboxylic group and a low acid value are used, and the probabilitythat the binder resin having a high acid value is present is increasedby a method such as phase separation from the central portion of thetoner toward the surface of the toner.

A yellow toner of the present invention contains 60.0 to 97.0 mass % ofa tetrahydrofuran (THF)-soluble component, and the THF-soluble componentcontains preferably 0.010 to 1.500 mass % of a sulfur element derivedfrom a sulfonic group. The toner of the present invention is moreexcellent in color development property than an ordinary toner, and canbe used in a reduced amount. The charging characteristic of the toner ispreferably set to be larger than that in an ordinary case in order thatthe amount of the toner to be used in development may be reduced.However, the addition of a large amount of a charge control agent to thetoner may reduce the color development property of the toner. When theTHF-soluble component of the toner of the present invention contains apredetermined amount of a sulfonic group, the charging characteristic ofthe toner can be improved without any reduction in color developmentproperty of the toner. In addition, the sulfonic group easily undergoesan interaction with the binder resin or any other additive in the tonersuch as a hydrogen bond or an ionic bond, so the color developmentproperty of the toner can be exerted in a particularly favorable manner.Meanwhile, the content of the THF-soluble component in the toner mayreduce owing to the polarity of the sulfonic group. Further, when animage is formed while the usage of the toner is reduced as compared toan ordinary case, the offset resistance, gloss uniformity, andpenetration resistance of the image are apt to reduce. When the contentof the THF-soluble component is less than 60.0 mass %, the colordevelopment property of the toner is apt to reduce. When the content ofthe THF-soluble component exceeds 97.0 mass %, the offset resistance,the gloss uniformity, and the penetration resistance are apt to reduce.In addition, when the content of the sulfur element is less than 0.010mass %, the extent to which the color development property of the toneris improved may be small. In addition, the amount of the toner to beused in development increases, so dot reproducibility reduces in somecases. When the content of the sulfur element exceeds 1.500 mass %, aninteraction between the sulfonic group and the colorant increases, sothe color development property of the toner reduces in some cases. Inaddition, the adsorptivity of the toner to a toner carrying member or anelectrostatic image bearing member become s large, and dotreproducibility reduces in some cases. It should be noted that thecontent of the above THF-soluble component is more preferably 70.0 to95.0 mass %, still more preferably 75.0 to 95.0 mass %, or particularlypreferably 80.0 to 93.0 mass %. In addition, the content of the abovesulfur element derived from the sulfonic group is more preferably 0.010to 0.500 mass %, still more preferably 0.010 to 0.150 mass %, orparticularly preferably 0.020 to 0.100 mass %.

A black toner of the present invention will be described.

A black toner of the present invention includes at least: a binderresin; and a colorant, wherein the black toner has a value (C_(K)) for ahue angle c* based on a CIELAB color coordinate system of 20.0 or less,an absorbance (A_(K600)) at a wavelength of 600 nm of 1.610 or more, anda ratio (A_(K600)/A_(K460)) of A_(K600) to an absorbance (A_(K460)) at awavelength of 460 nm of 0.970 to 1.035 in reflectance spectrophotometry.

The phrase “black toner has c*_(K) of 20.0 or less in the reflectancespectrophotometry” as used in the present invention means that the toneris a toner having a black color. When c*_(K) exceeds 20.0, the tonershows that a red color, a blue color, and other colors have highintensity.

In the case of the black toner having c*_(K) within the above range, thelarger A_(K600), the larger opacifying power the black toner has; ablack image having a high image density can be formed with a small toneramount. In addition, A_(K600)/A_(K460) is involved in the tinge of thetoner, and, when the ratio falls within the above range, a full-colorimage favorably expressing color development property even in asecondary color and a tertiary color and having a good color space canbe formed.

An increase in addition amount of the colorant in the black toner is aptto increase A_(K600). Meanwhile, A_(K600)/A_(K460) is apt to take avalue largely deviating from 1.000. When A_(K600)/A_(K460) is less than0.970, the black toner shows a strong red color, and a color space neara navy blue color in a secondary or tertiary color formed of a colortoner and the black toner becomes small. In addition, when the toner isused while a toner amount on paper is reduced, a red color becomesparticularly remarkable. When A_(K600)/A_(K460) exceeds 1.035, the blacktoner shows a strong blue color, and a color space near a dark browncolor in a secondary or tertiary color formed of a color toner and theblack toner becomes small. In addition, when the toner is used while atoner amount on paper is reduced, a blue color becomes particularlyremarkable. When A_(K600) is less than 1.610, a sufficient image densitycannot be obtained, or a toner amount on paper must be increased, so theeffects of the present invention such as a reduction in unevenness of animage surface and an improvement in dot reproducibility cannot beobtained.

According to the present invention, the value for A_(K600) describedabove is preferably large because a toner amount on paper can bereduced, and the effects of the present invention become large. However,the value for A_(K600) described above is preferably 2.100 or less inconsideration of a color balance when a full-color image is formed bycombining the black toner with any other color toner such as a cyantoner, a magenta toner, or a yellow toner, the color developmentefficiency of the colorant of the black toner, and a material cost. Therange of A_(K600) described above is more preferably 1.610 to 1.930,still more preferably 1.650 to 1.930, still more preferably 1.700 to1.920, or particularly preferably 1.700 to 1.920.

The range of the value for A_(K600)/A_(K460) described above is morepreferably 0.980 to 1.033, still more preferably 0.990 to 1.030, orparticularly preferably 0.998 to 1.025.

A_(K600) and A_(K600)/A_(K460) described above can each be controlleddepending on, for example, the kind and addition amount of the colorantin the toner, the state of presence of the colorant in the toner, thestate of presence of any other additive or the like, and the color of anadditive.

The black toner of the present invention has a ratio (A_(K460)/A_(K670))of A_(K460) to an absorbance (A_(K670)) at a wavelength of 670 nm ofpreferably 0.960 to 1.070 in the reflectance spectrophotometry. Anincrease in addition amount of the colorant in the toner is apt to causeA_(K460)/A_(K670) to take a value largely deviating from 1.000. WhenA_(K460)/A_(K670) is less than 0.960, the black toner is apt to show astrong red color, and a color space near a navy blue color in asecondary or tertiary color formed of a color toner and the black toneris apt to be small. In addition, when the toner is used while a toneramount on paper is reduced, a red color may become particularlyremarkable. When A_(K460)/A_(K670) exceeds 1.070, the black toner is aptto show a strong blue color, and a color space near a dark brown colorin a secondary or tertiary color formed of a color toner and the blacktoner is apt to be small. In addition, when the toner is used while atoner amount on paper is reduced, a blue color may become particularlyremarkable. Accordingly, the range of A_(K460)/A_(K670) described aboveis more preferably 0.970 to 1.050, or particularly preferably 0.975 to1.025.

A_(K460) described above is preferably 1.600 to 1.940. Setting A_(K460)within the range allows a relationship between the opacifying power ofthe black toner and a color balance when a color toner and the blacktoner are combined to be particularly favorably exerted. In the casewhere A_(K460) is less than 1.600, when the toner is used while a toneramount on paper is reduced, a color space near a dark brown color maybecome small. In the case where A_(K460) exceeds 1.940, when the toneris used while a toner amount on paper is reduced, a color space near anavy blue color is apt to be small. Accordingly, the range of A_(K460)is more preferably 1.650 to 1.940, or particularly preferably 1.700 to1.900.

Similarly, A_(K670) described above is preferably 1.580 to 1.940.Setting A_(K670) within the range allows a relationship between theopacifying power of the black toner and a color balance when a colortoner and the black toner are combined to be particularly favorablyexerted. In the case where A_(K670) is less than 1.580, when the toneris used while a toner amount on paper is reduced, a color space near anavy blue color may become small. In the case where A_(K670) exceeds1.940, when the toner is used while a toner amount on paper is reduced,a color space near a dark brown color is apt to be small. Accordingly,the range of A_(K670) is more preferably 1.640 to 1.920, or particularlypreferably 1.700 to 1.900.

The black toner of the present invention preferably has a value (a*_(K))for a* based on the CIELAB color coordinate system of −2.00 to 0.50, anda value (b*_(K)) for b* based on the system of −2.00 to 2.00 in thereflectance spectrophotometry. With such constitution, when a tonerconsumption is reduced, the representable color space of an imageadditionally expands, and the quality of the image becomes additionallygood. In the case where a*_(K) is less than −2.00, when a tonerconsumption is reduced, the color space of a portion having, forexample, a dark red color, a dark magenta color, or a dark purple colormay become small. In addition, in the case where a*_(K) exceeds 0.50,the color space of a portion having, for example, a dark blue color, adark cyan color, or a dark green color may become small. Accordingly,the range of a*_(K) is more preferably −1.65 to 0.10.

Similarly, in the case where b*_(K) is less than −2.00, the color spaceof a portion having, for example, a dark magenta color, a dark bluecolor, or a dark cyan color may become small. In the case where b*_(K)exceeds 2.00, the color space of a portion having, for example, a darkgreen color, a dark yellow color, or a dark red color may become small.Accordingly, the range of b*_(K) is more preferably −1.70 to 1.50, orparticularly preferably −1.50 to 1.20.

A black toner of the present invention has a viscosity (η_(K105)) at105° C. of 500 to 100,000 Pa·s, a viscosity (η_(K120)) at 120° C. of 100to 20,000 Pa·s, and a ratio (η_(K105)/η_(K120)) of η_(K105) to η_(K120)of preferably 3.0 to 50.0.

In the present invention η_(K105), η_(K120), and η_(K105)/η_(K120) showthe melt properties of the toner. The smaller η_(K105) or η_(K120), themore apt to melt and deform at a low temperature the toner is. Asη_(K105)/η_(K120) becomes closer to 1.0, a change in melt viscosity ofthe toner with temperature becomes smaller.

Since the black toner of the present invention has higher colordevelopment property than that of an ordinary toner, even when an imageis formed for one kind of image data with a smaller toner amount thanthat in the case where the ordinary toner is used, an image density andan image color gamut each of which is comparable to a conventional onecan be achieved. However, when one attempts to reduce a tonerconsumption by reducing the thickness of a toner layer of which theimage is formed, the toner penetrates into paper, and a fiber of thepaper is apt to be remarkable in an image portion unless the tonerretains some degree of viscosity in a fixing process. Alternatively, theappearance of the image is apt to reduce owing to a phenomenon such as areduction in chroma of the image. When the image is formed while a toneramount on the paper is reduced, the amount of a binder resin of whichthe image is constituted also reduces, so cold offset and hot offset areparticularly apt to occur. In view of the foregoing, the toner of thepresent invention, which is excellent in low-temperature fixability tosome extent, preferably retains an appropriate viscosity even at hightemperatures.

According to the present invention, when an image is formed while atoner amount on paper is reduced, the image is susceptible to moisturein the paper in the fixing step. Accordingly, in the present invention,a change in melt viscosity of the toner at 105 to 120° C. astemperatures each exceeding the boiling point of water is preferablycontrolled. In the case where η_(K105) described above exceeds 100,000Pa·s, or η_(K120) exceeds 20,000 Pa·s, when the toner is used while thetoner amount on the paper is reduced, cold offset is apt to occur. Inaddition, the color development property of the toner is notsufficiently exerted, and the representable color gamut of the imagereduces in some cases. In the case where η_(K105) is less than 500 Pa·s,or η_(K120) is less than 100 Pa·s, when the toner is used while thetoner amount on the paper is reduced, hot offset is apt to occur. Inaddition, the toner penetrates into the paper, the color gamut of theimage reduces, and a fiber of the paper becomes remarkable in an imageportion, with the result that the appearance of the image is apt toreduce.

In addition, in the case where η_(K105)/η_(K120) described above exceeds50.0, the toner penetrates into the paper, and the chroma of the imagereduces, or a fiber of the paper becomes remarkable in the imageportion, with the result that the appearance of the image is apt toreduce. In the case of duplex printing, the following problem may arise:an image on a front surface stands on a back surface. Further, hotoffset is apt to occur. In the case where η_(K105)/η_(K120) is less than3.0, cold offset is apt to occur, or the toner does not undergosufficient melting and deformation in the fixing step, so the colordevelopment property of the toner is not sufficiently exerted, and therepresentable color gamut of the image reduces in some cases. Further,the front end portion and rear end portion of the paper are apt todiffer from each other in image gloss or image color gamut with respectto the travelling direction of the paper in the fixing step, so theappearance of the image is apt to reduce.

Accordingly, the value for η_(K105) described above is more preferably500 to 50,000 Pa·s, or particular preferably 1,000 to 30,000 Pa·s.Similarly, the value for η_(K120) described above is more preferably 100to 10,000 Pa·s, or particularly preferably 400 to 5,000 Pa·s. Inaddition, η_(K105)/η_(K120) described above is more preferably 3.0 to25.0, or particularly preferably 5.0 to 20.0.

The black toner of the present invention has the highest endothermicpeak with a differential scanning calorimeter (DSC) at preferably 60 to140° C. The endothermic peak derives from the melting point of a wax inthe toner; the melting and deformation of the toner in the fixing stepare significantly promoted when the toner present in an image portion isheated to a temperature equal to or higher than the melting point of thewax. Accordingly, when a toner amount on paper is reduced, theendothermic peak is susceptible to the melting behavior of the wax inthe fixing step. In addition, in the case where a fixing process inwhich no oil application mechanism is present or only a trace amount ofoil is applied is employed in the fixing step, when an image is formedwhile a toner amount on paper is reduced, the amount of the tonerpresent on the paper is small, so the amount of the wax in a toner layerof which the image is constituted also reduces. Accordingly, when animage is formed for one kind of image data with a smaller toner amountthan that in the case where the ordinary toner is used, cold offset andhot offset are particularly apt to occur. When the temperature of thehighest endothermic peak is lower than 60° C., upon melting of the waxin the fixing step, the wax is apt to dissolve in the binder resin in alarge amount, and the melt viscosity of the toner is apt to reduce. As aresult, the value for η_(K105) or η_(K120) described above is apt todecrease, and the value for η_(K105)/η_(K120) described above is apt toincrease. In addition, upon melting of the wax in the fixing step, partof the wax dissolves in the binder resin, and the releasing performanceof the toner is apt to reduce. Accordingly, when the toner is used whileits consumption is reduced, hot offset is remarkably apt to occur. Onthe other hand, when the temperature of the highest endothermic peakexceeds 140° C., upon melting of the wax in the fixing step, the amountin which the wax dissolves in the binder resin is remarkably small, sothe plasticizing effect of the wax is hardly obtained. As a result, thevalue for η_(K105) or η_(K120) described above is apt to increase, andthe value for η_(K105)/η_(K120) described above is apt to decrease. Inaddition, a wax having the height endothermic peak at a temperature inexcess of 140° C. has large crystallinity, so, when a toner amount onpaper is reduced, a wax crystal to be mixed in a fixed image has asignificant influence on the representable color gamut of an image, andthe color gamut is apt to reduce. Accordingly, the highest endothermicpeak is placed at more preferably 60° C. to 95° C., or still morepreferably 65° C. to 90° C.

By the same reason as that described above, the half width of thehighest endothermic peak possessed by the black toner of the presentinvention is preferably 0.5 to 20.0° C. In addition, in the case where atoner amount on paper is reduced, when the half width exceeds 20.0° C.,gloss non-uniformity or density non-uniformity is apt to arise in animage at each of the former half portion and latter half portion of thedirection in which the paper is passed. When the half width is less than0.5° C., offset is apt to occur at the latter half portion of thedirection in which the paper is passed. Accordingly, the half width ismore preferably 1.0 to 15.0° C., or particularly preferably 2.0 to 10.0°C.

The black toner of the present invention can use a suitable colorant ina suitable addition amount so as to exert the reflection spectralcharacteristics. The addition amount of the colorant is preferably 8 to18 parts by mass with respect to 100 parts by mass of the binder resin.A coloring material is preferably incorporated in as small an amount aspossible into the toner in order that a running cost may be reduced.However, when the content of the colorant is less than 8 parts by mass,sufficient color development property may not be obtained. In addition,when the content of the colorant exceeds 18 parts by mass, therepresentable color space of an image may reduce.

In a black toner of the present invention, a relationship between anacid value (A_(K)1) of a first soluble component out of solvent-solublecomponents extracted from the black toner with isopropanol frominitiation of the extraction to 20 mass % with reference to a total massof the soluble components and an acid value (A_(K)2) of a second solublecomponent out of the solvent-soluble components in excess of 20 mass %to 100 mass % with reference to the total mass preferably satisfies thefollowing expression 7A _(K)1>A _(K)2  (Ex. 7).

In a developing device, the toner is apt to be damaged by a mechanicalstress from a toner carrying member, an electrostatic image bearingmember, or any other member. Part of the toner chips, or is broken, toproduce a fine powder in some cases. The fine powder adheres to any oneof the members to change the charging performance of the toner or tocontaminate paper directly, and image appearance is reduced in somecases. In particular, in the case of a black toner having high coloringpower like the toner of the present invention, the charging performanceof the toner is susceptible to a colorant even when a trace amount of afine powder adheres, and the extent to which paper is contaminated whena fine powder adheres to the paper is apt to be large. Accordingly, thecharging characteristic of the toner of the present invention ispreferably controlled more precisely than in the case of a conventionaltoner. In the present invention, the following procedure is preferablyadopted: the surface layer of a toner particle is provided with a resinlayer having a higher acid value than that of the inside of the tonerparticle, and the exposure of the colorant in the toner particle to atoner surface is suppressed. In addition, when the surface layer of thetoner particle is provided with the resin layer having a high acidvalue, a polar group derived from the acid value is considered to act asa charging auxiliary agent, so a charging failure hardly occurs. Whenthe acid value (A_(K)1) of a first soluble component out ofsolvent-soluble components extracted from the black toner of the presentinvention with isopropanol from the initiation of the extraction to 20mass % with reference to the total mass of the soluble components, thatis, a component the main component of which is considered to be a resinof which a toner surface layer is formed and the acid value (A_(K)2) ofa second soluble component out of the solvent-soluble components inexcess of 20 mass % to 100 mass % with reference to the total mass, thatis, a component the main component of which is considered to be a resinof which a toner core portion is formed satisfy the expression 7, thefirst component forms the toner surface layer, whereby the exposure ofthe colorant to a toner surface is suppressed, and the chargingperformance of the toner becomes additionally good by virtue of thepresence of a large amount of a resin having a large acid value on thetoner surface.

A_(K)1 described above is preferably 3.0 to 50.0 mgKOH/g. When A_(K)1 isless than 3.0 mgKOH/g, an improving effect on the charging performanceof the toner by virtue of the presence of a component having a high acidvalue on the surface of the toner is apt to be small. When A_(K)1exceeds 50.0 mgKOH/g, a polar group derived from the acid value of thecomponent and a polar group in the colorant interact with each other, sothe color development property of the toner reduces in some cases.Accordingly, A_(K)1 described above is particularly preferably 5.0 to30.0 mgKOH/g. In addition, by the same reason as that described above, adifference (A_(K)1-A_(K)2) between A_(K)1 and A_(K)2 is preferably 0.5to 30.0 mgKOH/g, or more preferably 2.0 to 20.0 mgKOH/g.

A_(K)1 and A_(K)2 described above can be controlled by using two or morekinds of resins having different acid values and controlling the statesof presence of the resins in the toner. To be specific, for example, anyone of the following methods can be employed: (1) a method involvingadding, to the toner, a charge control resin having a large acid valuethan that of the binder resin out of the charge control resins eachhaving a sulfonic group or a carboxylic group, (2) a method involvingforming, near the surface of the toner, a coat layer having a resinhaving a larger acid value than that of the binder resin out of theresins each having a sulfonic group or a carboxylic group, and (3) amethod in which a binder resin having a sulfonic group or a carboxylicgroup and a high acid value, and a binder resin having a sulfonic groupor a carboxylic group and a low acid value are used, and the probabilitythat the binder resin having a high acid value is present is increasedby a method such as phase separation from the central portion of thetoner toward the surface of the toner.

A black toner of the present invention preferably contains 60.0 to 97.0mass % of a tetrahydrofuran (THF)-soluble component, and the THF-solublecomponent contains 0.010 to 1.500 mass % of a sulfur element derivedfrom a sulfonic group. The toner of the present invention is moreexcellent in color development property than an ordinary toner, and canbe used in a reduced amount. The charging characteristic of the toner ispreferably set to be larger than that in an ordinary case in order thatthe amount of the toner to be used in development may be reduced.However, the addition of a large amount of a charge control agent to thetoner may reduce the color development property of the toner. When theTHF-soluble component of the toner of the present invention contains apredetermined amount of a sulfonic group, the charging characteristic ofthe toner can be improved without any reduction in color developmentproperty of the toner. In addition, the sulfonic group easily undergoesan interaction with the binder resin or any other additive in the tonersuch as a hydrogen bond or an ionic bond, so the color developmentproperty of the toner can be exerted in a particularly favorable manner.Meanwhile, the content of the THF-soluble component in the toner mayreduce owing to the polarity of the sulfonic group. Further, when animage is formed while the usage of the toner is reduced as compared toan ordinary case, the offset resistance, gloss uniformity, andpenetration resistance of the image are apt to reduce. When the contentof the THF-soluble component is less than 60.0 mass %, the colordevelopment property of the toner is apt to reduce. When the content ofthe THF-soluble component exceeds 97.0 mass %, the offset resistance,the gloss uniformity, and the penetration resistance are apt to reduce.In addition, when the content of the sulfur element is less than 0.010mass %, the extent to which the color development property of the toneris improved may be small. In addition, the amount of the toner to beused in development increases, so dot reproducibility reduces in somecases. When the content of the sulfur element exceeds 1.500 mass %, aninteraction between the sulfonic group and the colorant increases, sothe color development property of the toner reduces in some cases. Inaddition, the adsorptivity of the toner to a toner carrying member or anelectrostatic image bearing member becomes large, and dotreproducibility reduces in some cases. It should be noted that thecontent of the above THF-soluble component is more preferably 70.0 to95.0 mass %, still more preferably 75.0 to 95.0 mass %, or particularlypreferably 80.0 to 93.0 mass %. In addition, the content of the abovesulfur element derived from the sulfonic group is more preferably 0.010to 0.500 mass %, still more preferably 0.010 to 0.150 mass %, orparticularly preferably 0.020 to 0.100 mass %.

Next, the constitution of a toner preferable for exerting the effects ofthe present invention to the fullest extent possible will be described.The cyan toner, magenta toner, yellow toner, or black toner of thepresent invention preferably has a weight-average particle diameter (D4)of 1.5 to 7.5 μm, and a ratio (D4/D1) of D4 described above to a numberaverage particle diameter (D1) of 1.00 to 1.40. When D4 exceeds 7.5 μm,in the case of a toner excellent in color development property like thetoner of the present invention, the toner has so large opacifying powerthat the lightness and chroma of an image will be small in some cases ifa sufficient image density is obtained. In addition, the developmentfailure, transfer failure, and fixation failure of one toner particlehave so large influences on image appearance that, at the time ofcontinuous printing, an image in which coarseness is remarkable at ahalftone portion and a solid image portion fades is apt to be obtained.When the toner is crashed excessively in the fixing step, a dot or aline becomes thick, so faithfulness to image data is apt to reduce. Onthe other hand, in the case of a toner having D4 of less than 1.5 μm, atransfer failure is apt to be produced, and, when a toner amount onpaper is reduced, an image defect is remarkably apt to be produced. Inaddition, the toner transferred onto the paper is apt to crawl into afiber of the paper, and, when the toner amount on the paper is reduced,the toner is apt to penetrate into the paper in the fixing step.Accordingly, the toner of the present invention has D4 of morepreferably 2.5 to 6.5 μm, still more preferably 2.5 to 6.0 μm, orparticularly desirably 3.0 to 5.5 μm. When D4/D1 exceeds 1.40 as well,phenomena similar to those occurring when D4 described above exceeds 7.5μm and when D4 is less than 1.5 μm are apt to occur. Accordingly, D4/D1is more preferably 1.00 to 1.25, or still more preferably 1.00 to 1.20.

The toner for each color of the present invention contains tonerparticles each having a particle diameter more than twice as large asthe weight-average particle diameter (D4) at a content of preferably 25mass % or less. When the toner is used while a toner amount on paper isreduced, an influence of a toner particle having a particle diameterlargely deviating from the average particle diameter of the toner is aptto be large. When the content of toner particles each having a particlediameter more than twice as large as D4 exceeds 25.0 mass %, microscopicdensity non-uniformity is apt to arise in an image portion, and thechroma and lightness of an image are apt to reduce. The transfer failureor scattering of a coarse particle is also apt to show a remarkableimage failure, and the reproducibility of a dot or line is apt toreduce. Accordingly, the toner for each color of the present inventioncontains toner particles each having a particle diameter more than twiceas large as D4 of more preferably 15.0 mass % or less, or still morepreferably 10.0 mass % or less.

In addition, the toner for each color of the present invention containstoner particles each having a particle diameter less than one half ofthe number average particle diameter (D1) at a content of preferably30.0 number % or less. When the content of toner particles each having aparticle diameter less than one half of D1 exceeds 30.0 number %,electrostatic offset or the contamination of a member is apt to occur. Afine particle in such toner is apt to cause a transfer failure, and,when a toner amount on paper is reduced, an image defect becomesremarkable. In addition, the toner transferred onto the paper is apt tocrawl into a fiber of the paper, so an excessive amount of the toner isneeded for the formation of an image having a sufficient image density.Accordingly, the toner of the present invention contains toner particleseach having a particle diameter less than one half of D1 at a content ofmore preferably 20.0 number % or less, or still more preferably 10.0number % or less.

When the true density of the toner for each color of the presentinvention is represented by ρ_(T) (g/cm³), the endotherm (Q) of thehighest endothermic peak preferably falls within the range of(1.0×ρ_(T)) J/cm³ to (20.0×ρ_(T)) J/cm³. The endotherm serves as anindex showing the content of a wax in the toner. In order that a runningcost may be reduced, the content of the wax in the toner is preferablysmall, so a value for Q described above is preferably as small aspossible. However, in order that the toner may be used while a toneramount on paper is reduced, when Q is less than (1.0×ρ_(T)) J/cm³, theamount of the wax present on the paper becomes small in the fixing step,so sufficient releasing performance cannot be obtained, and offset isapt to occur. On the other hand, when Q exceeds (20.0×ρ_(T)) J/cm³, theendotherm of the toner is large, so, when the toner is used while atoner amount on the paper is reduced, cold offset is apt to occur.Further, the color development of a colorant in a toner layer isobstructed by the crystal of the wax in the toner at an image portion,and the chroma of an image reduces in some cases. Accordingly, the rangeof Q is more preferably (4.0×ρ_(T)) J/cm³ to (15.0×ρ_(T)) J/cm³, orparticularly preferably (6.0×ρ_(T)) J/cm³ to (10.0×ρ_(T)) J/cm³.

By the same reason as that described above, the toner for each color ofthe present invention contains the wax in an amount of preferably 3.0 to20.0 parts by mass, more preferably 4.0 to 15.0 parts by mass, or stillmore preferably 5.0 to 13.0 parts by mass with respect to 100 parts bymass of a binder resin.

The toner for each color of the present invention contains a componenthaving a molecular weight of 3,000 to 5,000 at a content of preferably3.0 to 40.0 area % in a molecular weight distribution by the gelpermeation chromatography (GPC) of a tetrahydrofuran (THF)-solublecomponent. In a developing device, the toner is apt to be damaged by amechanical stress from a toner carrying member, an electrostatic imagebearing member, or any other member. Part of the toner chips, or isbroken, to produce a fine powder in some cases. The fine powder adheresto any one of the members to change the charging performance of thetoner or to contaminate paper directly, and image appearance is reducedin some cases. In particular, in the case of a toner having highcoloring power like the toner of the present invention, the chargingperformance of the toner is susceptible to a colorant even when a traceamount of a fine powder adheres, and the extent to which paper iscontaminated when a fine powder adheres to the paper is apt to be large.On the other hand, when such toner having high coloring power as thatdescribed above is used while a toner amount on paper is reduced, coldoffset and hot offset are apt to occur. Alternatively, the tonerexcessively penetrates into the paper in the fixing step, with theresult that image gloss and an image color gamut are apt to reduce.Accordingly, the molecular weight of a binder resin of which the toneris mainly composed is preferably controlled more precisely than in anordinary case. When the content of the component having a molecularweight of 3,000 to 5,000 exceeds 40.0 area %, the crystallinity of thebinder resin becomes high, so the toner is apt to crack in a developingdevice, and the developing performance of the toner is apt to reduce atthe time of continuous printing. When the content of the componenthaving a molecular weight of 3,000 to 5,000 is less than 3.0 area %, thefixing performance of the toner reduces, and cold offset is apt tooccur. In addition, an affinity between the wax and the binder resinbecomes small, with the result that the toner is apt to crack with aninterface between the binder resin and the wax in the toner as a basepoint. Accordingly, the content of the component having a molecularweight of 3,000 to 5,000 is more preferably 5.0 to 40.0 area %, orparticularly preferably 8.0 to 35.0 area %.

By the same reason as that described above, the toner for each color ofthe present invention contains a component having a molecular weight of300 to 800 at a content of preferably 0.3 to 8.0 area % in the molecularweight distribution by the GPC of the THF-soluble component. When thecontent of the component having a molecular weight of 300 to 800 exceeds8.0 area %, the toner is apt to crack in a developing device, and thedeveloping performance of the toner is apt to reduce at the time ofcontinuous printing. In addition, the toner excessively penetrates intopaper, with the result that image gloss and an image color gamut are aptto reduce. When the content of the component having a molecular weightof 300 to 800 is less than 0.3 area %, the fixing performance of thetoner reduces, and cold offset is apt to occur. In addition, an affinitybetween the wax and the binder resin becomes small, with the result thatthe toner is apt to crack with an interface between the binder resin andthe wax in the toner as a base point. Accordingly, the content of thecomponent having a molecular weight of 300 to 800 is more preferably 0.3to 5.0 area %, or particularly preferably 0.5 to 3.5 area %.

The content of the component having a molecular weight of 3,000 to 5,000and the content of the component having a molecular weight of 300 to 800described above can each be controlled depending on the content of acomponent having any such molecular weight as described above in thebinder resin or any other additive in the toner. In addition, thecontents can each be controlled depending on heating conditions, coolingconditions, or decompression conditions at the time of kneading or apolymerization reaction. The contents can each be adjusted also bycontrolling, for example, the heating conditions and the coolingconditions with a surface modification apparatus.

It is also preferable to add a solvent capable of dissolving a resin tobe used as the binder resin or as any other additive such as toluene orxylene at the time of the production of the resin. The content of thecomponent having a molecular weight of 3,000 to 5,000 can be suitablyadjusted by reducing the viscosity of a reaction system to advance thepolymerization reaction quickly. In addition, the resin does notsolidify in the latter half of the polymerization reaction, so thepolymerization reaction can be sufficiently advanced, and the content ofthe component having a molecular weight of 300 to 800 can be suitablyadjusted.

When toner particles are produced by a polymerization method, thecontent of a component having any such molecular weight as describedabove can be adjusted by, for example, the addition amount of apolymerization initiator, a heating temperature during thepolymerization reaction, and a heating step and a decompression stepafter the polymerization reaction. It is also preferable that suchmethod and the method of adding the solvent be employed in combination.

When the toner particles are produced by a production method involvingthe use of a resin as a raw material such as: a wet granulation methodsuch as the so-called solution suspension; a dry granulation methodtypified by a kneading pulverization method; or a method involvingperforming granulation by drying a resin dissolved in a solvent such asa spray dry method, it is also preferable that the resin be washed witha solvent having a lower alcohol such as methanol or ethanol afterhaving been produced. When one attempts to increase the content of thecomponent having a molecular weight of 3,000 to 5,000 in the resin, thecontent of the component having a molecular weight of 300 to 800 is alsoapt to be large in association with the increase. Washing such resinwith the above solvent having a lower alcohol can reduce the content ofan unreacted monomer or oligomer, and allows the content of thecomponent having a molecular weight of 300 to 800 to be suitablyadjusted.

The toner for each color of the present invention has an averagecircularity of preferably 0.940 to 0.995. In a developing device, thetoner is apt to be damaged by a mechanical stress from a toner carryingmember, an electrostatic image bearing member, or any other member. Partof the toner chips, or is broken, to produce a fine powder in somecases. The fine powder adheres to any one of the members to change thecharging performance of the toner or to contaminate paper directly, andimage appearance is reduced in some cases. In particular, in the case ofa toner having high coloring power like the toner of the presentinvention, the charging performance of the toner is susceptible to acolorant even when a trace amount of a fine powder adheres, and theextent to which paper is contaminated when a fine powder adheres to thepaper is apt to be large. When the average circularity is less than0.940, a protruded portion of the toner is apt to chip, and an imagefailure is apt to be produced at the time of continuous printing. On theother hand, when the average circularity exceeds 0.995, an image defectis apt to be produced owing to a cleaning failure. Accordingly, theaverage circularity is more preferably 0.955 to 0.990, or particularlypreferably 0.965 to 0.988.

In addition, by the same reason as that described above, the toner foreach color of the present invention has a standard deviation ofcircularities of preferably 0.005 to 0.045. The reason for the foregoingis as described below. Any one of the toner particles of the toner ofthe present invention has larger color developing power than that of anordinary toner in order that a toner amount on paper may be reduced.Accordingly, the toner is susceptible to a toner particle having acircularity largely deviating from the value for the averagecircularity.

Examples of the wax to be used in the present invention include thefollowing. An aliphatic hydrocarbon-based wax such as alow-molecular-weight polyethylene, a low-molecular-weight polypropylene,an olefin copolymer, a microcrystalline wax, a paraffin wax, or aFischer-Tropsch wax; an oxide of the aliphatic hydrocarbon-based waxsuch as an oxidized polyethylene wax and block copolymers thereof; a waxmainly composed of an fatty acid ester such as a carnauba wax and amontanate wax; and a wax obtained by deoxidizing part of or whole fattyacid ester, such as a deoxidized carnauba wax.

Further examples include a saturated linear fatty acid such as palmiticacid, stearic acid, or montanic acid; an unsaturated fatty acid such asbrassidic acid, eleostearic acid, or parinaric acid; a saturated alcoholsuch as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubylalcohol, ceryl alcohol, or mericyl alcohol; a polyalcohol such assorbitol; a fatty acid amide such as amide linoleate, amide oleate, oramide laurate; a saturated fatty acid bisamide such as methylenebisamide stearate, ethylenebis amide caprate, ethylenebis amide laurate, orhexamethylenebis amide stearate; an unsaturated fatty acid amide such asethylenebis amide oleate, hexamethylenebis amide oleate, N,N′-dioleylamide adipate, or N,N′-dioleyl amide sebacate; an aromatic bisamide suchas m-xylenebis amide stearate or N,N′-distearyl amide isophthalate; afatty acid metal salt (which is generally referred to as “metal soap”)such as calcium stearate, calcium laurate, zinc stearate, or magnesiumstearate; a graft wax obtained by subjecting an aliphatic hydrocarbonwax to graft reaction with a vinyl monomer such as styrene or acrylicacid; a partial esterified product obtained from reaction of a fattyacid and a polyalcohol, such as monoglyceride behenate; and amethylester compound having a hydroxyl group, which is obtained byhydrogenating a vegetable oil.

The particularly preferred wax to be used in the present invention is analiphatic hydrocarbon-based wax. Preferred examples of the wax include:a low-molecular-weight olefin polymer obtained by radical polymerizationof an olefin under a high pressure or by polymerization of an olefinwith a Ziegler catalyst or a metallocene catalyst under a low pressure;Fisher-Tropsch wax synthesized from coal or natural gas; an olefinpolymer obtained by heat decomposition of a high-molecular-weight olefinpolymer; and a synthetic hydrocarbon wax obtained from a distillationresidue of a hydrocarbon obtained from a synthetic gas containing carbonmonoxide and hydrogen by the Arge method, or a synthetic hydrocarbon waxobtained by hydrogenation thereof. The hydrocarbon wax separated by apress sweating method, a solvent method, a vacuum distillation or afractional crystallization mode is more preferably used.

A hydrocarbon as a component for a hydrocarbon wax is preferably ahydrocarbon synthesized by a reaction between carbon monoxide andhydrogen using a metal oxide catalyst (multiple system composed of twoor more kinds in many cases) [such as a hydrocarbon compound synthesizedby a synthol method or a hydrocol method (involving the use of a fluidcatalyst bed)], a hydrocarbon having up to several hundreds of carbonatoms obtained by an Arge method (involving the use of an identificationcatalyst bed) with which a large amount of a wax-like hydrocarbon can beobtained, a hydrocarbon obtained by polymerizing an alkylene such asethylene with a Ziegler catalyst, or a paraffin wax because any suchhydrocarbon is a saturated, long linear hydrocarbon with a small numberof small branches. A wax synthesized by a method not involving thepolymerization of an alkylene is particularly preferable because of itsmolecular weight distribution.

The molecular weight of the wax is preferably as follows: a main peak ispresent in the molecular weight region of 350 to 2,000. The waxpreferably has a weight-average molecular weight of 400 to 3,000, and anumber average molecular weight of 300 to 1,800. Providing the wax withany such molecular weight can impart preferable heat characteristics tothe toner. The molecular weight of the wax can be adjusted depending onthe kind of the wax to be used and conditions under which the wax isproduced.

In the present invention, preferable production steps for the tonerinclude: a first kneading step (so-called master batch treatment) ofkneading raw materials to provide a first kneaded product; and a secondkneading step of kneading the first kneaded product and other addedmaterials to provide a finely dispersed colorant composition. The wax inthe present invention may be added simultaneously with materialsincluding a binder at the time of the second kneading step, but the waxis preferably added in advance in the state of a wax dispersant to aresin composition in order that a colorant may be dispersed in the tonerin an additionally fine fashion and a granular touch in a low-densityregion may be alleviated.

The wax dispersant contains the wax and a wax dispersion medium, and thewax dispersion medium, which is a product as a result of a reactionbetween polyolefin and a vinyl polymer, is more preferably obtained bygrafting the vinyl polymer to the polyolefin. In addition, a waxdispersant master batch obtained by melting and mixing the resultant waxdispersant and a polyester resin at an appropriate compounding ratio inadvance is more preferable because the extent to which the colorant isdispersed in the second kneading step is improved.

Hereinafter, the wax dispersant will be described in detail.

The wax dispersant desirably has a wax dispersion medium having atleast: a vinyl polymer synthesized by using one or two or more kinds ofvinyl monomers; and polyolefin.

Further, a “wax dispersant master batch” obtained by melting the waxdispersant and mixing the molten dispersant in a polyester resin isdesirably added in the second kneading step at the time of tonerproduction.

Examples of the vinyl monomer to be used as the wax dispersion mediuminclude: styrenes such as styrene, o-methylstyrene, m-methylstyrene,p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorstyrene,3,4-dichlorstyrene, p-ethylstyrene, 2,4-dimethylstyrene,p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene,p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene,p-n-dodecylstyrene, and derivatives thereof; α-methylene aliphaticmonocarboxylic acids and esters thereof such as methyl methacrylate,ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutylmethacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexylmethacrylate, stearyl methacrylate, phenyl methacrylate,dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate;acrylic esters such as methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecylacrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethylacrylate, and phenyl acrylate; and acrylate or methacrylate derivativessuch as acrylonitrile, methacrylonitrile, and acrylamide.

Further, examples of the vinyl monomer include: unsaturated dibasicacids such as maleic acid, citraconic acid, itaconic acid,alkenylsuccinic acid, fumaric acid, and mesaconic acid; unsaturateddibasic acid anhydrides such as maleic anhydride, citraconic anhydride,itaconic anhydride, and alkenylsuccinic anhydride; unsaturated basicacid half esters such as methyl maleate half ester, ethyl maleate halfester, butyl maleate half ester, methyl citraconate half ester, ethylcitraconate half ester, butyl citraconate half ester, methyl itaconatehalf ester, methyl alkenylsuccinate half ester, methyl fumarate halfester, and methyl mesaconate half ester; unsaturated basic acid esterssuch as dimethyl maleate and dimethyl fumarate; acid anhydrides ofα,β-unsaturated acids such as acrylic acid, methacrylic acid, crotonicacid, and cinnamic acid; α,β-unsaturated anhydrides such as crotonic andcinnamic anhydride and anhydrides of the above-mentioned α,β-unsaturatedacids and lower aliphatic acids; and monomers each having a carboxylgroup such as alkenylmalonic acid, alkenylglutaric acid, andalkenyladipic acid, and acid anhydrides thereof and monoesters thereof.

Further, examples of the vinly monomer include: acrylic esters ormathacrylic esters such as 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, and 2-hydroxypropyl methacrylate; and monomers each havinga hydroxyl group such as 4-(1-hydroxy-1-methylbutyl) styrene and4-(1-hydroxy-1-methylhexyl) styrene.

Of those, a copolymer of styrene and a nitrogen-containing acrylate ormethacrylate is particularly preferable.

In the molecular weight distribution of a wax dispersion medium havingat least a vinyl polymer synthesized by using a vinyl monomer andpolyolefin by GPC, a weight-average molecular weight (Mw) is preferably5,000 to 100,000, a number average molecular weight (Mn) is preferably1,500 to 15,000, and a ratio (Mw/Mn) of the weight-average molecularweight (Mw) to the number average molecular weight (Mn) is preferably 2to 40 because of the following reasons.

When the weight-average molecular weight (Mw) of the wax dispersionmedium is less than 5,000, the number average molecular weight (Mn) ofthe wax dispersion medium is less than 1,500, or the ratio (Mw/Mn) ofthe weight-average molecular weight (Mw) to the number average molecularweight (Mn) is less than 2, the storage stability of the toner may beaffected.

When the weight-average molecular weight (Mw) of the wax dispersionmedium exceeds 100,000, the number average molecular weight (Mn) of thewax dispersion medium exceeds 15,000, or the ratio (Mw/Mn) of theweight-average molecular weight (Mw) to the number average molecularweight (Mn) exceeds 40, the wax finely dispersed in the wax dispersantcannot rapidly migrate toward the surface of a molten toner at the timeof fixation and melting, and an effect of the wax cannot be sufficientlyexerted in some cases.

The polyolefin in the wax dispersion medium preferably has a localmaximum value for the highest endothermic peak at 80 to 140° C. in anendothermic curve at the time of temperature increase measured with aDSC.

When the local maximum value for the highest endothermic peak of thepolyolefin is placed at a temperature lower than 80° C. or at atemperature in excess of 140° C., in any case, a branched structure(graft) formed of the polyolefin and the copolymer synthesized by usinga vinyl monomer is lost. Accordingly, the hydrocarbon wax is not finelydispersed, and the segregation of the hydrocarbon wax occurs when atoner is produced, with the result that image failures such as blankdots may be produced. Examples of the polyolefin include polyethyleneand an ethylene-propylene copolymer; of those, in particular,low-density polyethylene is most preferably used in terms of theefficiency of a reaction between the copolymer and the polyolefin.

The tetrahydrofuran (THF)-soluble component in the toner for each colorof the present invention has an acid value of preferably 0.1 to 50.0mgKOH/g. Since the toner of the present invention has a large colorantcontent, the dispersing performance of a colorant in the toner is apt toreduce. However, setting the acid value of a binder resin within theabove range improves the dispersing performance of the colorant, andimproves the color development property and fixing performance of thetoner.

Any one of various resins known as conventional binder resins forelectrophotography is used as a binder resin to be used in the cyantoner, magenta toner, yellow toner, or black toner of the presentinvention. It is preferable that the binder resin be mainly composed ofa resin selected from (a) a polyester resin, (b) a hybrid resin having apolyester unit and a vinyl copolymer unit, (c) a mixture of a hybridresin and a vinyl copolymer, (d) a mixture of a hybrid resin and apolyester resin, (e) a mixture of a polyester resin and a vinylcopolymer, and (f) a mixture of a polyester resin, a hybrid resin havinga polyester unit and a vinyl copolymer unit, and a vinyl copolymer outof the various resins.

When a polyester resin is used as the binder resin, a polyhydric alcoholand, for example, a polycarboxylic acid, a polycarboxylic acidanhydride, or a polycarboxylate can be used as raw material monomers.

Examples of the dihydric alcohol component include: alkylene oxideadducts of bisphenol A such aspolyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene(3.3)-2,2-bis(4-hydroxyphenyl)propane,polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene(2.0)-polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane,and polyoxypropylene(6)-2,2-bis(4-hydroxyphenyl)propane; ethyleneglycol; diethylene glycol; triethylene glycol; 1,2-propyleneglycol;1,3-propyleneglycol; 1,4-butanediol; neopentyl glycol; 1,4-butenediol;1,5-pentanediol; 1,6-hexanediol; 1,4-cyclohexanedimethanol; dipropyleneglycol; polyethylene glycol; polypropylene glycol; polytetramethyleneglycol; bisphenol A; and hydrogenated bisphenol A.

Examples of the alcohol component having three or more hydroxyl groupsinclude sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol,dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol,1,2,5-pentanetriol, glycerol, 2-methylpropanetriol,2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and1,3,5-trihydroxymethylbenzene.

Examples of the polycarboxylic acid component include: aromaticdicarboxylic acids such as phtalic acid, isophtalic acid, andterephtalic acid, and anhydrides thereof; alkyldicarboxylic acids suchas succinic acid, adipic acid, sebacic acid, and azelaic acid, andanhydrides thereof; succinic acids substituted by an alkyl group having6 to 12 carbon atoms, and anhydrides thereof; unsaturated dicarboxylicacids such as fumaric acid, maleic acid, and citraconic acid, andanhydrides thereof; and n-dodecenylsuccinic acid and indodecenylsuccinicacid can be given.

Of those, in particular, a polyester resin obtained by condensationpolymerization using a bisphenol derivative represented by the followinggeneral formula (1) as a diol component and using a carboxylic acidcomponent of divalent carboxylic acid, anhydride thereof, or lower alkylester thereof (such as fumaric acid, maleic acid, maleic anhydride,phthalic acid, and terephthalic acid) as an acid component is preferredbecause the resin or unit serving as a color toner exhibits excellentcharging property.

Examples of the polycarboxylic acid component having three or morehydroxyl groups for forming a polyester resin having a crosslinking siteinclude 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylicacid, 1,2,4-naphthalenetricarboxylic acid,2,5,7-naphthalenetricarboxylic acid, 1,2,4,5-benzenetetracarboxylicacid, or anhydrides and ester compounds thereof.

The amount of the polycarboxylic acid component having three or morehydroxyl groups to be used is preferably 0.1 to 1.9 mol % based on theamount of total monomers. Moreover, in the case of using a hybrid resinincluding a polyester unit, which is a polycondensate of a polyhydricalcohol and a polybasic having ester bonds in a main chain, and a vinylpolymer unit, which is a polymer having an unsaturated hydrocarbon base,as the binder resin, further improved wax dispersibility and enhancedlow temperature fixability and offset resistance can be expected. Thehybrid resin used in the present invention refers to a resin in which avinyl polymer unit and a polyester unit are chemically bonded to eachother. Specifically, a polyester unit and a vinyl polymer unit obtainedby polymerizing a monomer having a carboxylate group such as a(meth)acrylate form the resin through an ester exchange reaction.Preferably, the polyester unit and the vinyl polymer form a graftcopolymer (or block copolymer) in which the vinyl polymer serves as abackbone polymer and the polyester unit serves as a branch polymer.

Examples of the vinyl monomers for forming the vinyl polymer include:styrene such as styrene, o-methylstyrene, m-methylstyrene,p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene,2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene,p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene,p-n-dodecylstyrene, p-methoxystyrene, p-chlorostyrene,3,4-dichlorostyrene, m-nitrostyrene, o-nitrostyrene, p-nitrostyrene, andderivatives thereof; unsaturated monoolefins such as ethylene,propylene, butylene, and isobutylene; unsaturated polyenes such asbutadiene and isoprene; vinyl halides such as vinyl chloride, vinylidenechloride, vinyl bromide, and vinyl fluoride; vinyl esters such as vinylacetate, vinyl propionate, and vinyl benzoate; α-methylene aliphaticmonocarboxylates such as methyl methacrylate, ethyl methacrylate, propylmethacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octylmethacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearylmethacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, anddiethylaminoethyl methacrylate; acrylates such as methyl acrylate, ethylacrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octylacrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate,2-chloroethyl acrylate, and phenyl acrylate; vinyl ethers such as vinylmethyl ether, vinyl ethyl ether, and vinyl isobutyl ether; vinyl ketonessuch as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenylketone; N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole,N-vinylindole, and N-vinylpyrrolidone; vinylnaphthalenes; and acrylateor methacrylate derivatives such as acrylonitrile, methacrylonitrile,and acrylamide.

Further, examples of the vinyl monomers for forming the vinyl polymerinclude: unsaturated dibasic acids such as maleic acid, citraconic acid,itaconic acid, alkenylsuccinic acid, fumaric acid, and mesaconic acid;unsaturated dibasic acid anhydrides such as maleic anhydride, citraconicanhydride, itaconic anhydride, and alkenylsuccinic anhydride;unsaturated dibasic acid half esters such as maleic acid methyl halfester, maleic acid ethyl half ester, maleic acid butyl half ester,citraconic acid methyl half ester, citraconic acid ethyl half ester,citraconic acid butyl half ester, itaconic acid methyl half ester,alkenylsuccinic acid methyl half ester, fumaric acid methyl half ester,and mesaconic acid methyl half ester; unsaturated dibasic acid esterssuch as dimethyl maleate and dimethyl fumarate; α,β-unsaturated acidssuch as acrylic acid, methacrylic acid, crotonic acid, and cinnamicacid; α,β-unsaturated anhydrides such as crotonic anhydride and cinnamicanhydride; anhydrides of the above-mentioned α,β-unsaturated acids andlower aliphatic acids; and monomers each having a carboxyl group such asalkenylmalonic acid, alkenylglutaric acid, and alkenyladipic acid, acidanhydrides thereof, and monoesters thereof.

Further, examples of the vinyl monomers for forming the vinyl polymerinclude: acrylates or methacrylates such as 2-hydroxyethyl acrylate,2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate; andmonomers having hydroxy groups such as4-(1-hydroxy-1-methylbutyl)styrene and4-(1-hydroxy-1-methylhexyl)styrene.

In the toner for each color of the present invention, the vinyl polymerunits of binder resins may have a crosslinking structure crosslinkedwith a crosslinking agent having two or more vinyl groups. Examples ofthe crosslinking agent to be used in this case include: aromatic divinylcompounds such as divinylbenzene and divinylnaphthalene; diacrylatecompounds bonded together with an alkyl chain, such as ethylene glycoldiacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate,1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycoldiacrylate, and those obtained by changing the “acrylate” of each of theaforementioned compounds to “methacrylate”; diacrylate compounds bondedtogether with an alkyl chain containing an ether bond, such asdiethylene glycol diacrylate, triethylene glycol diacrylate,tetraethylene glycol diacrylate, polyethylene glycol #400 diacrylate,polyethylene glycol #600 diacrylate, dipropylene glycol diacrylate, andthose obtained by changing the “acrylate” of each of the aforementionedcompounds to “methacrylate”; and diacrylate compounds bonded togetherwith a chain containing an aromatic group and an ether bond, such aspolyoxyethylene(2)-2,2-bis(4-hydroxyphenyl)propane diacrylate,polyoxyethylene(4)-2,2-bis(4-hydroxyphenyl)propane diacrylate, and thoseobtained by changing the “acrylate” of each of the aforementionedcompounds to “methacrylate”.

Examples of the polyfunctional crosslinking agents include:pentaerythritol triacrylate, trimethylolethane triacrylate,trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate,oligoester acrylate, and those obtained by changing the “acrylate” ofthe aforementioned compounds to “methacrylate”; and triallyl cyanurateand triallyl trimellitate.

When the hybrid resin is used in the present invention, at least one ofa vinyl polymer unit and a polyester unit preferably contains a monomercomponent capable of reacting with both the resin components. Examplesof a monomer capable of reacting with the vinyl polymer unit among themonomers each constituting the polyester unit include unsaturated dicarboxylic acids such as phthalic acid, maleic acid, citraconic acid,and itaconic acid, and anhydrides of the acids. Examples of a monomercapable of reacting with the polyester unit among the monomers eachconstituting the vinyl polymer unit include vinyl monomers each having acarboxyl group or a hydroxyl group, and acrylates or methacrylates.

A method of obtaining a product as a result of a reaction between avinyl polymer unit and a polyester unit is preferably a method involvingsubjecting one or both resin of the above-mentioned vinyl polymer unitand polyester unit to a polymerization reaction in the presence of apolymer containing a monomer component capable of reacting with each ofthe units.

Examples of the polymerization initiators to be used in the productionof the vinyl polymer of the present invention include2,2′-azobisisobutyronitrile,2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-methylbutyronitrile), dimethyl-2,2′-azobisisobutyrate,1,1′-azobis(1-cyclohexanecarbonitrile),2-(carbamoylazo)-isobutyronitrile, 2,2′-azobis(2,4,4-trimethylpentane),2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile,2,2′-azobis(2-methylpropane), ketone peroxides such as methyl ethylketone peroxide, acetylacetone peroxide, and cyclohexanone peroxide,2,2-bis(t-butylperoxy)butane, t-butyl hydroperoxide, cumenehydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t-butylperoxide, t-butylcumyl peroxide, dicumyl peroxide,α,α′-bis(t-butylperoxyisopropyl)benzene, isobutyl peroxide, octanoylperoxide, decanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoylperoxide, benzoyl peroxide, m-toluoyl peroxide, diisopropylperoxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-n-propylperoxydicarbonate, di-2-ethoxyethyl peroxycarbonate, dimethoxyisopropylperoxydicarbonate, di(3-methyl-3-methoxybutyl) peroxycarbonate,acetylcyclohexylsulfonyl peroxide, t-butyl peroxyacetate, t-butylperoxyisobutyrate, t-butyl peroxyneodecanoate, t-butylperoxy-2-ethylhexanoate, t-butyl peroxylaurate, t-butyl peroxybenzoate,t-butylperoxyisopropyl carbonate, di-t-butyl peroxyisophthalate, t-butylperoxyallylcarbonate, t-amyl peroxy-2-ethylhexanoate, di-t-butylperoxyhexahydroterephthalate, and di-t-butyl peroxyazelate.

Examples of a method of preparing a hybrid resin to be used in the tonerfor each color of the present invention include the following methodsdescribed in the items (1) to (6).

(1) An ester compound can be used as the hybrid resin component, whichis synthesized by separately producing a vinyl polymer and a polyesterresin, dissolving and swelling the vinyl polymer and the polyester resinin a small amount of organic solvent, adding an esterification catalystand alcohol to the solution, and heating the mixture to carry out anester exchange reaction.

(2) A method in which a polyester unit and a hybrid resin component areproduced in the presence of a vinyl polymer after the production of thevinyl polymer. The hybrid resin component is produced by a reactionbetween the vinyl polymer unit (a vinyl-based monomer may be added asrequired) and one or both of a polyester monomer (for example, alcoholor a carboxylic acid) and polyester. An organic solvent can be used asappropriate in this case as well.

(3) A method in which a vinyl polymer and a hybrid resin component areproduced in the presence of a polyester unit after the production of thepolyester unit. The hybrid resin component is produced by a reactionbetween one or both of the polyester unit (a polyester monomer may beadded as required) and a vinyl-based monomer.

(4) A method of producing a hybrid resin component including: producinga vinyl polymer unit and a polyester unit; and adding one or both of avinyl-based monomer and a polyester monomer (for example, alcohol or acarboxylic acid) in the presence of those polymer units. An organicsolvent can be used as appropriate in this case as well.

(5) A method in which, after the production of a hybrid resin component,one or both of a vinyl-based monomer and a polyester monomer (forexample, alcohol or a carboxylic acid) is added to carry out one or bothof addition polymerization and a condensation polymerization reaction tothereby produce a vinyl polymer unit and a polyester unit. In this case,a hybrid resin component produced by any one of the production methodsdescribed in the above items (2) to (4) can also be used, and also oneproduced by a known production method can be used as required. Inaddition, an organic solvent can be used as appropriate.

(6) A method in which a vinyl-based monomer and a polyester monomer (forexample, alcohol or a carboxylic acid) are mixed to successively carryout addition polymerization and a condensation polymerization reactionto thereby produce a vinyl polymer unit, a polyester unit, and a hybridresin component. In addition, an organic solvent can be used asappropriate.

In each of the production methods described in the above items (1) to(5), multiple polymer units different from each other in molecularweight and in degree of crosslinking can be used for each of the vinylpolymer unit and the polyester unit.

It should be noted that a mixture of the above polyester resin and avinyl polymer, a mixture of the above hybrid resin and a vinyl polymer,or a mixture of the above polyester resin, the above hybrid resin, and avinyl polymer may be used as the binder resin to be incorporated intothe toner for each color of the present invention.

The toner for each color of the present invention has tetrahydrofuran(THF)-insoluble matter at a content of preferably 5 to 90 mass %, morepreferably 5 to 70 mass %, or still more preferably 5 to 50 mass %. Thisis because a balance between storage stability or development stabilityand low-temperature fixability is additionally improved.

In the present invention, an available charge control agent to beincorporated in the toner may be any of those known in the art. Inparticular, a metallic compound of an aromatic carboxylic acid ispreferred because it has no color, has a high toner charge speed, andcan maintain a constant charge amount stably.

Examples of a negative charge control agent to be used include ametallic compound of salicylic acid, a metallic compound of naphthoicacid, a metallic compound of dicarboxylic acid, a high-molecularcompound having sulfonic acid or carboxylic acid in the side chain, aboron compound, a urea compound, a silicon compound, and a calixarene.Examples of a positive charge control agent to be used include aquaternary ammonium salt, a high-molecular compound having thequaternary ammonium salt in the side chain, a guanidine compound, and animidazole compound. Of those, aluminium 3,5-di-tert-butylsalicylate isparticularly preferred because it exhibits rapid rise in charge amount.The charge control agent may be added to toner particles internally orexternally. The amount of the charge control agent to be added ispreferably 0.5 to 10 parts by mass with respect to 100 parts by mass ofa binder resin.

Of those, a compound having the following characteristics is preferable:the compound has a sulfonic group and an amide bond, has, between thesulfonic group and the amide bond, an alkyl, ether, or aryl group having1 to 12 carbon atoms, and has an amide sulfonic group. Specific examplesof the compound include compounds each having an amide sulfonic grouprepresented by the following general formula (2).[Chem 2]A1-B1-SO₃R1  (2)(In the formula, B1 represents an aromatic ring, alkyl group having 2 to12 carbon atoms, or ether group having 2 to 12 carbon atoms which mayhave a substituent, and the substituent is a hydrogen atom, a hydroxylgroup, or an alkyl, aryl, or alkoxy group having 1 to 12 carbon atoms,R1 represents a hydrogen atom, an alkali metal ion, a quaternaryammonium ion, or an alkyl or aryl group having 1 to 12 carbon atoms, andA1 represents an amide bond.)

As the compound having a sulfonic amide group, a copolymer of a sulfonicgroup-containing (meth)acrylamide and another vinyl monomer ispreferably exemplified. Specific examples of preferable sulfonicgroup-containing (meth)acrylamide include 2-acrylamide-2-methylpropanesulfonic acid, its alkali salts, 2-acrylamide-2-methylpropane methylsulfonate, 2-acrylamide-2-methylpropane ethyl sulfonate,2-acrylamide-2-methylpropane propyl sulfonate, and a compoundrepresented by the following general formula (3).

(In the formula, R2 represents a hydrogen atom or a methyl group, R3 toR6 each independently represent a hydrogen atom, a hydroxyl group, or analkyl or alkoxy group having 1 to 6 carbon atoms, and two adjacentgroups of R3 to R6 may form a five- or six-membered aromatic ring, andR7 represents an alkyl group having 1 to 4 carbon atoms.)

When the compound having an amide sulfonic group is a resin having anamide sulfonic group, the content of monomer units each containing anamide sulfonic group in the resin is preferably 1.0 to 30.0 mol %.

In toner particles each containing a resin where the monomer units eachcontaining an amide sulfonic group are present in an appropriate amount,the balance of the charge of the toner and the balance of the dispersionof an internal additive can be appropriately adjusted. When the contentof the monomer units each containing an amide sulfonic group in theresin is less than 1 mol %, an effect of a sulfonic group may not besufficiently exerted. On the other hand, when the content exceeds 30 mol%, the charge of the toner is apt to be non-uniform, and fogging or thelike is apt to occur.

The content of an amide sulfonic compound in the toner for each color ofthe present invention is preferably 0.5 to 15.0 mass % with respect tothe entirety of the toner. The presence of an appropriate amount of theamide sulfonic compound in the toner allows the charge of the toner orthe balance of the dispersion of an internal additive to beappropriately adjusted. When the content is less than 0.5 mass %, aneffect of a sulfonic group may not be sufficiently exerted. On the otherhand, when the content exceeds 15.0 mass %, the amount in which sulfonicgroups are present in the toner is so large that an effect of any otherinternal additive may be small.

In the present invention, a known additive can be externally added toeach of the toner particles; it is particularly preferable that afluidity improver be externally added in terms of an improvement inimage quality and storage stability under a high-temperatureenvironment. An inorganic fine powder made of, for example, silica,titanium oxide, or aluminum oxide is a preferable fluidity improver. Theinorganic fine powder is preferably made hydrophobic with a hydrophobicagent such as a silane compound or silicone oil, or a mixture of them.

Examples of the hydrophobic agent include: coupling agents such as asilane compound, a titanate coupling agent, an aluminium coupling agent,and a zircoaluminate coupling agent.

Specifically, a compound represented by the general formula (4) ispreferable as the silane compound. Examples of the silane compoundinclude hexamethyldisilazane, vinyltrimethoxysilane,vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane,methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane,dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane,hydroxypropyltrimethoxysilane, phenyltrimethoxysilane,n-hexadecyltrimethoxysilane, and n-octadecyltrimethoxysilane. The amountto be made hydrophobic is preferably 1 to 60 parts by mass, morepreferably 3 to 50 parts by mass with respect to 100 parts by mass ofthe inorganic unhydrophobed powder.[Chem 4]R_(m)SiY_(n)  General formula (4)[In the formula, R represents an alkoxy group, m represents an integerof 1 to 3, Y represents an alkyl group, a vinyl group, a phenyl group, amethacryl group, an amino group, an epoxy group, a mercapto group, orderivatives thereof, and n represents an integer of 1 to 3]

In the present invention, of those fluidity improvers, analkylalkoxysilane represented by a general formula (5) is particularlysuitably used in a hydrophobic treatment for the surface of theinorganic fine powder. The case where n represents less than 4 in thealkylalkoxysilane is not preferable because the treatment can be easilyperformed, but the extent to which the surface is made hydrophobic islow. When n represents more than 12, the surface shows sufficienthydrophobicity, but the frequency at which titanium oxide fine particlescoalesce increases, and the fluidity-improving ability of the improveris apt to reduce. When m represents more than 3, the reactivity of thealkylalkoxysilane reduces, so it becomes difficult to make the surfacehydrophobic favorably. It is more preferable that, in thealkylalkoxysilane, n represent 4 to and m represent 1 or 2. Thetreatment amount of the alkylalkoxysilane is preferably 1 to 60 parts bymass, or more preferably 3 to 50 parts by mass with respect to 100 partsby mass of the inorganic fine powder.[Chem 5]C_(n)H_(2n+1)—Si—(OC_(m)H_(2m+1))₃  General formula (5)[In the formula, n represents an integer of 4 to 12, and m represents aninteger of 1 to 3.]

The fluidity improver may be subjected to a hydrophobic treatment withone kind of a hydrophobic agent alone, or may be subjected to ahydrophobic treatment with two or more kinds of hydrophobic agents usedin combination. For example, the agent may be subjected to a hydrophobictreatment with one kind of a hydrophobic agent alone. Alternatively, theagent may be subjected to a hydrophobic treatment with two or more kindsof hydrophobic agents simultaneously, or may be subjected to ahydrophobic treatment with one kind of a hydrophobic agent and thensubjected to an additional hydrophobic treatment with anotherhydrophobic agent.

The fluidity improver is added in an amount of preferably 0.01 to 5parts by mass, or more preferably 0.05 to 3 parts by mass with respectto 100 parts by mass of the toner particles.

A cyan colorant that can be used in the present invention is, forexample, a copper phthalocyanine or a derivative of the compound, ananthraquinone compound, or abase dye lake compound. A colorant that canbe particularly suitably utilized is, specifically, C.I. Pigment Blue 1,2, 3, 7, 15, 15:1, 15:2, 15:3, 15:4, 16, 17, 60, 62, or 66, C.I. VatBlue 6, C.I. Acid Blue 45, a copper phthalocyanine pigment having astructure represented by the following general formula (6), or the like.

(In the general formula (6), X1 to X4 each represent

or —H, and R and R′ each represent an alkylene group having 1 to 5carbon atoms provided that the case where all of X1 to X4 each represent—H is excluded.)

To be specific, for example, a compound represented by a formula (7) canbe used as a compound represented by the above general formula.

Examples of a magenta colorant include a condensed azo compound, adiketopyrrolopyrrole compound, anthraquinone, a quinacridone compound, abasic dye lake compound, a naphthol compound, a benzimidazolonecompound, a thioindigo compound, and a perylene compound. Specifically,particularly preferred examples of the magenta colorant include: C.I.Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144,146, 150, 166, 169, 177, 184, 185, 202, 206, 220, and 22254; and C.I.Pigment Violet 19.

Examples of a yellow colorant include a condensed azo compound, anisoindolinone compound, an anthraquinone compound, an azo metal complex,a methine compound, and an allylamide compound. Specifically, preferredexamples of the yellow colorant include C.I. Pigment Yellow 12, 13, 14,15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129,147, 155, 168, 174, 176, 180, 181, and 191.

Examples of a black colorant include carbon black and any known metallicoxide, or the above-mentioned cyan, magenta, and yellow colorants.Examples of the metallic oxide include a metallic oxide containing anelement such as iron, cobalt, nickel, copper, magnesium, manganese,aluminum, or silicon. Of those, a metallic oxide mainly containing aniron oxide such as iron oxide black, γ-iron oxide, iron titaniumcomposite oxide, and iron aluminium composite oxide is preferable. Themetallic oxide may contain a metallic element such as a silicon element,an aluminum element, or sodium element from the standpoint ofcontrolling chargeability of the toner. The metallic oxide has a BETspecific surface area by nitrogen adsorption of preferably 2 to 30 m²/g,particularly preferably 3 to 28 m²/g, and have a Mohs hardness ofpreferably 5 to 7.

Examples of the shape of the metallic oxide include an octahedral shape,a hexahedral shape, a spherical shape, an acicular shape, and a scalyshape. The metallic oxide preferably has a shape with a low degree ofanisotropy such as the octahedral shape, the hexahedral shape, or thespherical shape in order to increase an image density. The averageparticle size of the metallic oxide is preferably 0.05 to 1.0 μm, morepreferably 0.1 to 0.6 μm, and still more preferably 0.1 to 0.4 μm.

Reflection spectral characteristics suitable for each toner can beadjusted by mixing those colorants.

In the case of a toner having high coloring power like the presentinvention, two or more kinds of colorants are preferably used as amixture in order that the charging performance of the toner at the timeof continuous printing may be retained at a favorable level.

A fine powder selected from a silica fine powder, an alumina finepowder, a titania fine powder, and a composite oxide is preferably usedfor improving charging stability, developing performance, fluidity, andstorage stability. The silica fine powder is particularly good. Drysilica produced by the vapor-phase oxidation of a silicon halide oralkoxide, and wet silica produced from an alkoxide, water glass, and thelike can each be used as silica; the dry silica is more preferablebecause the number of silanol groups present on its surface or in asilica fine powder is small, and the amount of a production residue suchas Na₂O or SO₃ ²⁻ is small. In the dry silica, a composite fine powderof silica and any other metal oxide can be obtained by using a metalhalide compound such as aluminum chloride or titanium chloride and asilicon halide compound in combination in a production step for the drysilica, and the composite fine powder may be used.

The average circularity of the toner for each color of the presentinvention can be adjusted also by using a surface modification apparatusto be described later.

The toner for each color of the present invention can be produced by awet production method such as a suspension polymerization method, anagglomeration melt adhesion method, a solution suspension method, or adispersion polymerization method as well as a dry production method suchas a kneading pulverization method.

As the specific production method by kneading pulverization method, abinder resin, a colorant, wax, and such other arbitrary material,cooling and grinding the kneaded product, rounding and classifying theground products as required, followed by mixing in of theabove-described fluidity improver.

First, in a raw material mixing step, predetermined amounts of at leastresin and a colorant are weighted, and then compounded and mixedtogether as agents to be internally added to the toner. Examples of amixing device include a double con mixer, a V-type mixer, a drum-typemixer, a Super mixer, a Henschel mixer, and a nauta mixer.

Further, the toner raw materials compounded and mixed as described aboveare melted and kneaded to melt the resin, and the colorant and the likeare dispersed in the melted resin. In the melting and kneading step, forexample, a batch kneader such as a pressure kneader, a Banbury mixer,etc or a continuous kneader can be used. Recently, due to the advantageof allowing continuous production, a single-screw or twin-screw extruderis becoming mainstream. For example, a KTK series twin-screw extruderfrom KOBE STEEL, LTD., a TEM series twin-screw extruder from TOSHIBAMACHINE CO., LTD., a twin-screw extruder from KCK Corporation, aco-kneader from Buss Co., Ltd., and the like are generally used. Theprecolored resin composition obtained by melting and kneading the tonerraw materials is rolled out by two rolls or the like after the meltingand kneading step, and then cooled through a cooling step of cooling thecomposition by water cooling or the like.

Subsequently, the resulting cooled product of the precolored resincomposition obtained as described above is usually ground into apredetermined particle size by a grinding step. In the grinding step,first, the precolored resin composition is roughly ground with acrusher, a hammer mill, a feather mill, or the like, followed by furthergrinding with a Criptron system from Kawasaki Heavy Industries, Ltd., aSuper Rotor from Nisshin Engineering, or the like. Subsequently, theground products are classified by using a screen classifier, forexample, a classifier such as an Elbow-Jet classifier (from NITTESUMINING CO., LTD.) employing an inertia classification system, aTurboplex classifier (from HOSOKAWA MICRON CORPORATION) employing acentrifugal classification system, etc, to obtain toner particles.

As required, surface modification and rounding may be performed in thesurface modification step by using, for example, a hybritization systemfrom NARA MACHINERY CO., LTD., or a mechanofusion system from HOSOKAWAMICRON CORPORATION.

According to the present invention, it is preferable that no mechanicalgrinding be performed in the grinding step, and that a device thatperforms classification and surface modification treatment using amechanical impact force be used after grinding with an air jet typegrinding machine to thereby obtain toner particles. The surfacemodification treatment and the classification may be performedseparately, in which case a screen classifier such as HIBOLTA that is awind screen (from Shin Tokyo Kikai Corporation) may be used. Inaddition, examples of a method of externally adding external additivesinclude compounding predetermined amounts of the classified toner andknown various external additives and then stirring and mixing them byusing as an external adding machine a high-speed stirrer that applies ashearing force to powder, such as a Henschel mixer, a Super mixer, orthe like.

FIG. 7 shows an example of a surface modifying device used in thepresent invention.

The surface modifying device shown in FIG. 7 includes: a casing 55; ajacket (not shown) through which cooling water and an anti-freezesolution can pass; a classifying rotor 41 as classifying means forclassifying between particles having sizes larger than a predeterminedparticle size and fine particles having sizes smaller than thepredetermined particle size; a dispersing rotor 46 as surface treatmentmeans for treating the surface of the above-mentioned particles byapplying a mechanical impact to the particles; liners 44 arrangedcircumferentially on an outer periphery of the dispersing rotor 46 at apredetermined interval; a guide ring 49 as guiding means for guiding,from among the particles classified by the classifying rotor 41, theparticles having sizes larger than the predetermined size to thedispersing rotor 46; a discharge port for collecting fine powders 42 asdischarging means for discharging, from among the particles classifiedby the classifying rotor 41, the fine particles having sizes smallerthan the predetermined particle size to the outside; a cold airintroduction port 45 as particle circulation means for sending theparticles having their surfaces treated by the dispersing rotor 46 tothe classifying rotor 41; a raw material supply port 43 for introducingthe treated particles into the casing 55; and a powder discharge port 47and a discharge valve 48, which are openable and closable, fordischarging the surface-treated particles from the casing 55.

The classifying rotor 41 is a cylindrical rotor and is provided on oneend surface side inside the casing 55. The fine powder collectiondischarge port 42 is provided on one end portion of the casing 55 sothat particles present inside the classification rotor 41 are dischargedtherefrom. The raw material supply port 43 is provided in a centralportion of a circumferential surface of the casing 55. The cold airintroduction port 45 is provided on the other end surface side on thecircumferential surface of the casing 55. The powder discharge port 47is provided on the circumferential surface of the casing 55 at aposition opposite to the raw material supply port 43. The dischargevalve 48 is a valve capable of freely opening and closing the powderdischarge port 47.

The dispersing rotor 46 and the liner 44 is provided between the coldair introduction port 45 and the raw material supply port 43 and betweenthe cold air introduction port 45 and the powder discharge port 47,respectively. The liner 44 is arranged circumferentially along an innerperipheral surface of the casing 55. As shown in FIG. 8, the dispersingrotor 46 includes a circular disk and plural square disks 50 arrangednormal to the circular disk along the outer edge of the circular disk.The dispersion rotor 46 is provided on the other end surface side of thecasing 55 and arranged such that a predetermined gap is formed betweenthe liner 44 and each square disk 50. The guide ring 49 is provided inthe central portion of the casing 55. The guide ring 49 is a cylindricalmember provided so as to extend from a position where it covers a partof the outer peripheral surface of the classifying rotor 41 to thevicinity of the classifying rotor 41. By means of the guide ring 49, theinterior of the casing 55 is divided into a first space 51 sandwichedbetween the outer peripheral surface of the guide ring 49 and the innerperipheral surface of the casing 55, and a second space 52 definedinside the guide ring 49.

Note that the dispersing rotor 46 may include cylindrical pins insteadof the square disks 50. While in this embodiment the liner 44 has alarge number of grooves provided on its surface opposing the square disk50, the liner 44 used may not have such grooves on its surface. Also,the classifying rotor 41 may be installed either vertically as shown inFIG. 7 or horizontally. In addition, one classifying rotor 41 may beprovided as shown in FIG. 7, or two or more classifying rotors 41 may beprovided.

In the surface modifying device constructed as described above, when anarticle to be finely ground is introduced from the raw material supplyport 43 with the discharged valve 48 being in the “closed” state, first,the introduced article to be finely ground is sucked in by a blower (notshown) and then subjected to classification by the classifying rotor 41.At this time, fine powders classified as having particle sizes equal toa predetermined particle size or smaller pass through thecircumferential surface of the classifying rotor 41 to be introducedinto the inside of the classifying rotor 41, and then continuouslydischarged and removed from the device to the exterior. Coarse powdershaving particle sizes equal to or larger than the predetermined particlesize are carried on a circulation flow generated by the dispersion rotor46 while moving along an inner periphery (second space 52) of the guidering 49 due to a centrifugal force, to be introduced to the gap(hereinafter also referred to as the “surface modification zone”)between the square disk 50 and the liner 44. The powders introduced intothe surface modification zone are subjected to surface modification byreceiving a mechanical impact force between the dispersing rotor 46 andthe liner 44.

The surface-modified powder particles are carried on cold air passingthrough inside the machine, to be also transported along the outerperiphery (first space 51) of the guide ring 49 to reach the classifyingrotor 41. By the classifying rotor 41, the fine powers are discharged tothe outside of the machine whereas the coarse powders are returned againto the second space 52 where the surface modifying operation is repeatedtherefor. In this way, with the surface modifying device of FIG. 7, theclassification of particles using the classifying rotor 41 and thesurface treatment of the particles using the dispersing rotor 46 arerepeated. Then, after a given period of time has elapsed, the dischargevalve 48 is opened to collect the surface-modified particles from thedischarge port 47.

Upon examination, it is preferable to adjust a period of time from theintroduction of the article to be finely ground, until the opening ofthe discharge valve (cycle time) and the rpm of the dispersing rotor incontrolling an average roundness of toner particles and an amount of waxpresent on the toner surface. To increase the average roundness, it iseffective to make the cycle time longer or increase a peripheral speedof the dispersing rotor. Further, to restrain the amount of the surfacereleasing agent used, conversely, it is effective to make the cycle timeshorter or to lower the peripheral speed. In particular, unless thecircumferential speed of the dispersion rotor is equal to or larger thana certain value, the pulverized products cannot be subjected toefficient sphering, so the pulverized products must be subjected tosphering with the cycle time lengthened. The circumferential speed ispreferably 1.2×10⁵ mm/sec or more, and the cycle time is preferably 5 to60 seconds from the viewpoint of the appropriate adjustment of theamount in which the wax is present on the surface of the toner and theaverage circularity of the toner.

When the toner is produced by a wet production method in the presentinvention, a known surfactant, or known organic or inorganic dispersantcan be used as a dispersion stabilizer. Of those, an inorganicdispersant can be preferably used because of the following reason: sincethe inorganic dispersant shows dispersion stability by virtue of itssteric hindrance, the stability hardly collapses even when a reactiontemperature is changed, and the inorganic dispersant can be easilywashed. Examples of such inorganic dispersant include: polyvalent metalphosphates such as calcium phosphate, magnesium phosphate, aluminumphosphate, and zinc phosphate; carbonates such as calcium carbonate andmagnesium carbonate; inorganic salts such as calcium metasilicate,calcium sulfate, and barium sulfate; and inorganic oxides such ascalcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica,bentonite, and alumina.

One kind alone, or a combination of two more kinds, of those inorganicdispersants is used in an amount of preferably 0.2 to 20 parts by masswith respect to 100 parts by mass of a polymerizable monomer. 0.001 to0.1 part by mass of a surfactant may be used in combination when oneaims to obtain an additionally fine toner having an average particlediameter of 5 μm or less.

Examples of the surfactant include sodium dodecylbenzenesulfate, sodiumtetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate,sodium oleate, sodium laurate, sodium stearate, and potassium stearate.

Although each of those inorganic dispersants may be used as it is, theparticles of each of the inorganic dispersants can be produced in anaqueous medium in order that additionally fine particles may beobtained. For example, in the case of calcium phosphate, water-insolublecalcium phosphate can be produced by mixing an aqueous solution ofsodium phosphate and an aqueous solution of calcium chloride underhigh-speed stirring, and dispersion with additional uniformity andadditional fineness can be attained.

In the suspension polymerization method, additives including a releaseagent composed of a low-softening substance, a colorant, a chargecontrol agent, and a polymerization initiator are added into, forexample, a polymerizable monomer, and are uniformly dissolved ordispersed in the monomer with a dispersing machine such as a homogenizeror an ultrasonic dispersing machine, whereby a polymerizable monomercomposition is produced. The polymerizable monomer composition isdispersed in an aqueous phase containing a dispersion stabilizer with anordinary stirring machine, homomixer, or homogenizer so that the dropletparticles of the polymerizable monomer composition are produced in theaqueous phase. The particles are polymerized, and are subjected to, forexample, filtration, washing, drying, and classification as required. Inthe suspension polymerization method, in order that the dropletparticles of the polymerizable monomer composition may each have adesired toner particle size, granulation is preferably performed while astirring speed and a stirring time are adjusted. After that, stirringhas only to be performed to such an extent that the particle states aremaintained and the sedimentation of the particles is prevented by virtueof the action of the dispersion stabilizer. A polymerization temperatureis 40° C. or higher, or generally 50 to 90° C.

The toner of the present invention can be used as a one-componentdeveloper, or can be used as a two-component developer having the tonerof the present invention and a carrier.

When the toner for each color of the present invention is used in atwo-component developer, the toner is preferably used in a developerhaving the toner and a carrier having a 50% particle diameter on avolume basis (D50) of 10.0 to 50.0 μm.

In a developing device, the toner is apt to be damaged by a mechanicalstress from the carrier, an electrostatic image bearing member, or anyother member. In particular, a stress from the carrier has a significantinfluence on the toner, and part of the toner chips, or is broken, toproduce a fine powder in some cases. The fine powder adheres to anyoneof the members to change the charging performance of the toner or tocontaminate paper directly, and image appearance is reduced in somecases. In particular, in the case of a toner having high coloring powerlike the toner of the present invention, the charging performance of thetoner is susceptible to a colorant even when a trace amount of a finepowder adheres, and the extent to which paper is contaminated when afine powder adheres to the paper is apt to be large. When D50 of thecarrier exceeds 50.0 μm, a ratio of the toner to be used in developmentto the toner carried by the carrier reduces, so the toner is apt tocrack in a developing device. In addition, when the toner is used whilea toner amount on paper is reduced, a dot or line in an image is apt tochip, or a solid image portion in the image is apt to fade. When D50 ofthe carrier is less than 10.0 μm, the developer is apt to be packed in adeveloping device, and the toner is apt to crack. When a toner havinglarge coloring power like the toner of the present invention is used, afine powder generated by the chipping of the toner has so large aninfluence on the charging performance of the toner that an image failureis apt to be produced in continuous printing. Accordingly, D50 of thecarrier is more preferably 10.0 to 45.0 μm, still more preferably 15.0to 40.0 μm, or particularly desirably 15.0 to 35.0 μm.

By the same reason as that described above, the carrier in thetwo-component developer has a content of a carrier having a particlediameter more than twice as large as D50 in the volume distribution ofpreferably 25.0% or less. When the content of the carrier exceeds 25.0%,a ratio of the toner to be used in development to the toner carried bythe carrier reduces, so the toner is apt to crack in a developingdevice. In addition, when the toner is used while a toner amount onpaper is reduced, a dot or line in an image is apt to chip, or a solidimage portion in the image is apt to fade. Accordingly, the content ismore preferably 15.0% or less, or still more preferably 10.0% or less.

In addition, the carrier in the two-component developer has a content ofa carrier having a particle diameter less than one half of D50 in thevolume distribution of preferably 30.0% or less. When the content of thecarrier exceeds 30.0%, the developer is apt to be packed in a developingdevice, and the toner is apt to crack. When a toner having largecoloring power like the toner of the present invention is used, a finepowder generated by the chipping of the toner has so large an influenceon the charging performance of the toner that an image failure is apt tobe produced in continuous printing. Accordingly, the content is morepreferably 20.0% or less, or still more preferably 15.0% or less.

The 50% particle diameter on a volume distribution basis (D50) of thecarrier, the content of the carrier having a particle diameter more thantwice as large as D50, and the content of the carrier having a particlediameter less than one half of D50 described above can each be measuredwith a dry or wet laser diffraction type particle size distributionmeter as long as the meter has a measuring range from submicrons toseveral hundreds of microns. To be specific, for example, a laserdiffraction type particle size distribution measuring device SALD-3000(manufactured by Shimadzu Corporation) can be used in the measurement.

An element selected from, for example, iron, copper, zinc, nickel,cobalt, manganese, and chromium elements can be used alone as thecarrier that can be used in the invention. Alternatively, a carrierconstituted in a composite ferrite state can be used. The shape of thecarrier is a spherical shape, a flat shape, or an amorphous shape, and acarrier of any one of the shapes can be used. Further, even a finestructure characterizing the surface of the carrier (such as surfaceunevenness) is preferably controlled. In general, the following methodhas been employed: the above inorganic oxide is calcined and granulatedso that carrier core particles are produced, and then the particles areeach coated with a resin. In order that the burden of the carrier on thetoner may be alleviated, a low-density dispersed carrier obtained bykneading an inorganic oxide and a resin, pulverizing the kneadedproduct, and classifying the pulverized products, or a carrier having atrue spherical shape formed by directly polymerizing a kneaded productof an inorganic oxide and a monomer in an aqueous medium is alsopreferably used.

A coated carrier obtained by coating the surface of the above carrierwith a resin is particularly preferable. A method involving dissolvingor suspending the resin in a solvent and applying the solution or thesuspension to the carrier to cause the solution or the suspension toadhere to the carrier, or a method involving merely mixing a resinpowder and the carrier to cause the powder and the carrier to adhere toeach other is applicable to the production of the coated carrier.

A coat material for the surface of the carrier varies depending on amaterial for the toner; examples of the coat material includepolytetrafluoroethylene, a monochlorotrifluoroethylene polymer,polyvinylidene fluoride, a silicone resin, a polyester resin, a styreneresin, an acrylic resin, polyamide, polyvinyl butyral, and an aminoacrylate resin, and one kind of them may be used alone, or multiplekinds of them may be used. The treatment amount of the above coatingmaterial for the carrier core particles is preferably 0.01 to 30 mass %(more preferably 0.05 to 20 mass %).

The carrier has an intensity of magnetization measured in a magneticfield of 10,000/4π (kA/m) (10,000 Oe) (σ₁₀₀₀₀) of preferably 25 to 100Am²/kg. In a developing device, the toner is apt to be damaged by amechanical stress from the carrier, an electrostatic image bearingmember, or any other member. In particular, a stress from the carrierhas a significant influence on the toner, and part of the toner chips,or is broken, to produce a fine powder in some cases. The fine powderadheres to any one of the members to change the charging performance ofthe toner or to contaminate paper directly, and image appearance isreduced in some cases. In particular, in the case of a toner having highcoloring power like the toner of the present invention, the chargingperformance of the toner is susceptible to a colorant even when a traceamount of a fine powder adheres, and the extent to which paper iscontaminated when a fine powder adheres to the paper is apt to be large.When σ₁₀₀₀₀ of the carrier exceeds 100 Am²/kg, the toner receives alarge stress in a developer magnetic brush, so the toner is apt to crackin a developing device. When σ₁₀₀₀₀ of the carrier is less than 25Am²/kg, the charging performance of the toner is apt to be reduced evenby a trace amount of a fine powder adhering to the carrier owing to thecracking of the toner, so the stability of an image density at the timeof continuous printing is apt to reduce. Accordingly, σ₁₀₀₀₀ describedabove is more preferably 40 to 90 Am²/kg, or particularly preferably 50to 70 Am²/kg.

The intensity of magnetization (σ₁₀₀₀₀) of the carrier can be adjustedby appropriately selecting the kind and amount of a magnetic substanceto be incorporated.

The intensity of magnetization (σ₁₀₀₀₀) of the carrier can be measuredwith, for example, a vibration magnetic field-type magnetic propertyautomatic recorder BHV-30 (manufactured by Riken Denshi. Co., Ltd.). Aspecific measurement method is as described below. A cylindrical plasticcontainer is densely filled with the carrier to a sufficient extent.Meanwhile, an external magnetic field of 10,000/4π (kA/m) (10,000 Oe) isgenerated. In the state, the magnetizing moment of the carrier withwhich the container is filled is measured. Further, the actual mass ofthe carrier with which the container is filled is measured, and theintensity of magnetization of the carrier (Am²/kg) is determined.

The carrier has an average circularity (C_(C)) of preferably 0.750 to0.990. The average circularity (C_(C)) is a coefficient showing theextent to which the shape of the carrier is close to a round shape, andthe average circularity is determined from the largest diameter andmeasured particle projected area of a particle. When the averagecircularity is 1.000, all carrier particles are each of a true sphericalshape, and, as the value decreases, the particles are each of anadditionally elongated or amorphous shape. In a developing device, thetoner is apt to be damaged by a mechanical stress from the carrier, anelectrostatic image bearing member, or any other member. In particular,a stress from the carrier has a significant influence on the toner, andpart of the toner chips, or is broken, to produce a fine powder in somecases. The fine powder adheres to any one of the members to change thecharging performance of the toner or to contaminate paper directly, andimage appearance is reduced in some cases. In particular, in the case ofa toner having high coloring power like the toner of the presentinvention, the charging performance of the toner is susceptible to acolorant even when a trace amount of a fine powder adheres, and theextent to which paper is contaminated when a fine powder adheres to thepaper is apt to be large. When C_(C) described above is less than 0.750,a stress is apt to converge on the toner present at a protruded portionof the carrier, so the toner is apt to crack. When C_(C) described aboveexceeds 0.990, the developer is apt to be packed in a developing device,and the toner is apt to crack. Accordingly, C_(C) described above ismore preferably 0.800 to 0.990, still more preferably 0.850 to 0.980, orparticularly desirably 0.870 to 0.950.

In addition, by the same reason as that described above, the coefficientof variation (C_(CV)) of the circularity distribution of the carrier ona volume basis is preferably 0.5 to 20.0%. The larger the coefficient ofvariation, the larger the extent to which the shape of the carrierchanges. When C_(CV) exceeds 20.0%, a stress is apt to converge on thetoner present at a protruded portion of the carrier, so the toner is aptto crack. When C_(CV) described above is less than 0.5%, the developeris apt to be packed in a developing device, and the toner is apt tocrack. Accordingly, C_(CV) described above is more preferably 0.5 to15.0%, still more preferably 0.5 to 12.0%, or particularly preferably1.0 to 10.0%. It should be noted that the coefficient of variationC_(CV) can be determined from the following expression.Coefficient of variation C _(CV)(%)=(standard deviation ofcircularites/D50)×100

The average circularity C_(C) and the coefficient of variation C_(CV) ofthe circularity distribution can each be measured with, for example, aMulti-Image Analyzer (manufactured by Beckman Coulter, Inc).

A specific measurement method is as described below. A solution preparedby mixing an aqueous solution of NaCl having a concentration of about 1%and glycerin at 50 vol %: 50 vol % is used as an electrolyte solution.Here, the aqueous solution of NaCl has only to be prepared by usingfirst grade sodium chloride, or, for example, an ISOTON (registeredtrademark)-II (manufactured by Coulter Scientific Japan, Co.) can beused as the aqueous solution. Glycerin has only to be a reagent grade orfirst grade reagent.

0.1 to 1.0 ml of a surfactant (preferably an alkylbenzene sulfonate) asa dispersant is added to the electrolyte solution (about 30 ml).Further, 2 to 20 mg of a measurement sample are added to the mixture.The electrolyte solution in which the sample has been suspended issubjected to a dispersion treatment with an ultrasonic dispersing unitfor about 1 minute, whereby a dispersion liquid is obtained.

By using a 200-μm aperture as an aperture and a lens having amagnification of 20, the circle-equivalent diameter and the circularityare calculated under the following condition.

Average brightness in measurement frame: 220 to 230, measurement framesetting: 300, threshold (SH): 50, binarization level: 180

The electrolyte solution and the dispersion liquid are charged into aglass measurement container, and the concentration of the carrier in themeasurement container is set to 5 to 10 vol %. The contents in the glassmeasurement container are stirred at the maximum stirring speed. Asuction pressure for the sample is set to 10 kPa. When the carrier hasso large a specific gravity as to be apt to sediment, a time period forthe measurement is set to 15 to 30 minutes. In addition, the measurementis suspended every 5 to 10 minutes, and the container is replenishedwith the sample liquid and the mixed solution of the electrolytesolution and glycerin.

Number of particles to be measured is 2,000. After the completion of themeasurement, blurred images, agglomerated particles (multiple particlesare simultaneously subjected to measurement), and the like are removedfrom a particle image screen with software in the main body of theapparatus.

The circularity and the circle-equivalent diameter of the carrier arecalculated from the following equation.Circularity=(4×Area/(MaxLength²×π)Circle-equivalent diameter=(4·Area/π)^(1/2)  [Formula 2]

The term “Area” as used herein is defined as the projected area of abinarized particle image, while the term “MaxLength” as used herein isdefined as the maximum diameter of the particle image of the carrier. Acircle-equivalent diameter is represented as the diameter of a truecircle when the “Area” is regarded as the area of the true circle. Theresultant individual circle-equivalent diameters are classified into 256divisions ranging from 4 to 100 μm, and are plotted on a logarithmicgraph on a volume basis.

The carrier has a true specific gravity of preferably 2.0 to 6.0 g/cm³.In a developing device, the toner is apt to be damaged by a mechanicalstress from the carrier, and part of the toner chips, or is broken, toproduce a fine powder in some cases. The fine powder adheres to thecarrier to change the charging performance of the toner or tocontaminate paper directly, and image appearance is reduced in somecases. In particular, in the case of a toner having high coloring powerlike the toner of the present invention, the charging performance of thetoner is susceptible to a colorant even when a trace amount of a finepowder adheres, and the extent to which paper is contaminated when afine powder adheres to the paper is apt to be large. When the truespecific gravity of the carrier exceeds 6.0 g/cm³, the toner receives alarge stress in a developer magnetic brush, so the toner is apt to crackin a developing device. When the true specific gravity of the carrier isless than 2.0 g/cm³, the charging performance of the toner is apt to bereduced even by a trace amount of a fine powder adhering to the carrierowing to the cracking of the toner, so the stability of an image densityat the time of continuous printing is apt to reduce. Accordingly, thetrue specific gravity is more preferably 2.0 to 5.5 g/cm³, still morepreferably 2.0 to 5.0 g/cm³, or particularly preferably 2.5 to 4.3g/cm³.

As described later, the true specific gravity of the carrier can bemeasured with, for example, a dry automatic densimeter Autopycnometer(manufactured by Yuasa Ionics Inc.).

The carrier is preferably a magnetic fine particle-dispersed resincarrier having a binder resin and a magnetic substance. The above binderresin is preferably a thermosetting resin. The above-mentioned physicalproperties can be suitably achieved, and, when a toner having largecoloring power is used like the present invention, an influence of thecolorant in the toner can be reduced.

Examples of the heat-curable resin composition include a phenol resin,an epoxy resin, a polyimide-based resin, a melamine resin, an urearesin, an unsaturated polyester resin, an alkyd resin, a xylene resin,an acetoguanamine resin, a furan resin, a silicone-based resin, apolyimide resin, and a urethane resin. Each of the above-describedresins may be used alone or two or more of them may be used incombination, but preferably contains at least a phenol resin.

A ratio “binder resin:magnetic fine particles” between a binder resin ofwhich composite particles in the present invention are each constitutedand magnetic fine particles is preferably 1:99 to 1:50 on a mass basis.

The carrier possessed by the two-component developer of the presentinvention may be coated with a coupling agent or a resin as required.

Any known resin can be used as the coat resin. Examples of the resininclude an epoxy resin, a silicone resin, a polyester resin, a fluorineresin, a styrene resin, an acrylic resin, and a phenol resin. A polymerobtained by polymerizing a monomer is also permitted. In considerationof durability and anti-contamination, a silicone resin is preferable.The treatment amount of the coat resin is preferably 0.01 to 3.0 partsby mass, or more preferably 0.1 to 2.0 parts by mass with respect to 100parts by mass of carrier cores in order that the above characteristicsmay be obtained.

In particular, a phenol resin is used as a binder resin for each of thecomposite particles, an epoxy group-containing silane coupling agent isused as a lipophilic treatment agent for each of the magnetic fineparticles, and a silicone resin is used as a coat resin for each of thecomposite particles (carrier cores). In addition, an aminogroup-containing silane coupling agent is preferably incorporated intothe silicone resin, or an amino group-containing silane coupling agentis preferably used as a pre-treatment agent before the compositeparticles are each coated with the resin. With such constitution, theamino group-containing silane coupling agent hydrolyzes by virtue ofmoisture moderately adsorbing to the inside of the phenol resin toundergo self-condensation while forming a hydrogen bond with a hydroxylgroup of the phenol resin, or to condense with a remaining silanol groupin the silicone resin to form a strong coating. At the same time, anamino group and an epoxy group of the lipophilic treatment agent foreach of the magnetic fine particles react with each other, whereby theadhesiveness of the silicone resin is improved, and the flaking or thelike of the coat resin is suppressed.

Next, a method of producing the magnetic fine particle-dispersed resincarrier will be described.

The composite particles can be produced by, for example, the so-calledpolymerization method involving: dispersing the magnetic fine particles(non-magnetic inorganic compound fine particles as required) in amonomer of which the binder resin is constituted; adding an initiator ora catalyst to the dispersed product; and dispersing the mixture in, forexample, an aqueous medium to polymerize the mixture, or the so-calledkneading pulverization method involving pulverizing the binder resincontaining the magnetic fine particles. The polymerization method ispreferable in order that the particle diameter of the carrier may beeasily controlled and a sharp particle size distribution may beobtained.

Composite particles each using a phenol resin as a binder resin can beproduced by, for example, a method involving: dispersing, in an aqueousmedium, phenols, aldehydes, and magnetic fine particles each subjectedto a lipophilic treatment; and adding a basic catalyst to the mixture tocause them to react with one another. A method of forming the so-calleddenatured phenol resin involving mixing phenols with a natural resinsuch as rosin, or a drying oil such as a wood oil or a linseed oil tocause them to react with each other is also permitted.

The binder resin is particularly preferably a phenol resin because ofthe following reason: the resin retains adsorbed water to a moderateextent, so the hydrolysis of a coupling agent is promoted, and a strongcoating can be formed.

Composite particles each using an epoxy resin as a binder resin can beproduced by, for example, a method involving: dispersing, in an aqueousmedium, bisphenols, epihalohydrin, and magnetic fine particles eachsubjected to a lipophilic treatment; and causing them to react with oneanother in an alkali aqueous medium.

Composite particles each using a melamine resin as a binder resin can beproduced by, for example, a method involving: dispersing, in an aqueousmedium, melamines, aldehydes, and magnetic fine particles each subjectedto a lipophilic treatment; and causing them to react with one another inthe presence of a weak acid catalyst.

A method of producing composite particles each using any otherthermosetting resin is, for example, a method involving: kneadingmagnetic fine particles each subjected to a lipophilic treatment withvarious resins; pulverizing the kneaded product; and subjecting thekneaded products to a sphering treatment.

Composite particles composed of magnetic fine particles each subjectedto a lipophilic treatment and a binder resin are treated with heat asrequired in some cases in order that the resin may be additionallycured. The heat treatment is particularly preferably performed underreduced pressure or an inert atmosphere in order that the magnetic fineparticles may be prevented from oxidizing.

When the composite particles are each coated with a coupling agent, amethod involving: dissolving the coupling agent in water or a solventaccording to an ordinary method; immersing the composite particles inthe solution; and filtrating and drying the resultant, or a methodinvolving: spraying the composite particles with an aqueous solution ofthe coupling agent or a solution of the coupling agent in a solventwhile stirring the composite particles; and drying the compositeparticles is employed. The method involving treating the compositeparticles while stirring the composite particles is particularlypreferable in order that the composite particles may be prevented fromcoalescing and a uniform coat layer may be formed.

The surface of each of the composite particles has only to be coatedwith a resin by a known method, and, for example, any one of a methodinvolving mixing the composite particles and the resin with a stirringmachine such as a Henschel mixer or a high-speed mixer, a methodinvolving impregnating the composite particles with a solvent containingthe resin, and a method involving spraying the composite particles withthe resin by using a spray dryer is available.

Next, a full-color image-forming method of the present invention will bedescribed.

The present invention relates to a full-color image-forming methodincluding the steps of: forming electrostatic images on a chargedelectrostatic image bearing member; developing the formed electrostaticimages with toners to form toner images; transferring the formed tonerimages onto a transfer material; and fixing the transferred toner imagesto the transfer material to form fixed images, in which: the step offorming the toner images includes a step of performing development witha first toner selected from a black toner, a cyan toner, a magentatoner, and a yellow toner to form a first toner image, a step ofperforming development with a second toner except the first tonerselected from the black toner, the cyan toner, the magenta toner, andthe yellow toner to form a second toner image, a step of performingdevelopment with a third toner except the first toner and the secondtoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a third toner image, and a step ofperforming development with a fourth toner except the first toner, thesecond toner, and the third toner selected from the black toner, thecyan toner, the magenta toner, and the yellow toner to form a fourthtoner image; and the cyan toner is a cyan toner containing at least abinder resin and a colorant, and the cyan toner has a value (h*_(C)) fora hue angle h* based on a CIELAB color coordinate system of 210.0 to270.0, an absorbance (A_(C470)) at a wavelength of 470 nm of 0.300 orless, an absorbance (A_(C620)) at a wavelength of 620 nm of 1.500 ormore, and a ratio (A_(C620)/A_(C670)) of A_(C620) to an absorbance(A_(C670)) at a wavelength of 670 nm of 1.00 to 1.25 in reflectancespectrophotometry.

According to such full-color image-forming method, an image color gamutcomparable to or better than a conventional one can be represented, agood-appearance image with reduced surface unevenness can be obtained,and a running cost can be suppressed as a result of a reduction inconsumption of the cyan toner. Further, a toner amount to be used in thedevelopment of the toner images on the electrostatic image bearingmember can be reduced, so toner scattering in the transferring step canbe suppressed, and toner images faithful to the electrostatic images canbe formed on the transfer material. The deformation of each of the tonerimages on the transfer material is suppressed in the transferring step,so fixed images faithful to the electrostatic images can be formed. Inaddition, a toner amount on a transfer material can be reduced, so, evenwhen paper much thinner than a conventional one such as paper for anadvertisement folded in a newspaper is used as a transfer material, afixation failure or the winding of the paper around a fixing unit issuppressed, and an image with small surface unevenness can be formed.

The reason for the foregoing is as described below. Since a cyan tonerhaving specific reflection spectral characteristics and more excellentin color development property than a conventional toner is used, a toneramount per unit area needed for representing an image color gamut and acolor space each of which is comparable to or better than a conventionalone for certain image data can be reduced as compared to a conventionalcyan toner. As a result, the amount of the cyan toner to be used in thedevelopment of certain image data on a unit area of the electrostaticimage bearing member can be reduced. The toner amount per unit area issmall, but the area of an electrostatic image to be formed on theelectrostatic image bearing member is constant, so the height of a tonerimage developed on the electrostatic image bearing member with the tonercan be reduced. According to the investigation conducted by theinventors of the present invention, the height of a toner image on theelectrostatic image bearing member and the ease with which a tonerscatters in the transferring step establish a proportional relationship.Accordingly, reducing the above height of the toner image suppresses thescattering of the toner, and allows the toner image on the electrostaticimage bearing member to be transferred onto the transfer material withadditional faithfulness. The effect is more significant in the case ofan image-forming method involving the use of an intermediate transferbody, and is particularly significant when the intermediate transferbody is used twice or more.

In general, a toner image transferred onto a transfer material undergoesa fixing step so that a fixed image is formed. According to theinvestigation conducted by the inventors of the present invention, theheight of an unfixed toner image on the transfer material and the easewith which the toner image spreads in a transferring step establish aproportional relationship. That is, even if a high-definition,high-resolution toner image is formed on the transfer material, when thetoner image has a high height, the resolution of a fixed image reducesowing to the melt spread or rolling of toner in the fixing step. In thefull-color image-forming method of the present invention, the height ofa cyan toner image on the transfer material can be reduced, so aphenomenon such as the melt spread or rolling of toner in the fixingstep is suppressed, and hence a fixed toner image faithful to theunfixed toner image on the transfer material can be formed.

Those effects are exerted irrespective of whether the fixing step is ofa contact type or a non-contact type. When the fixing step is based on aheat fixing system, those effects are particularly significant; in thecase of a fixing step based on a heat pressure system, a suppressingeffect on the rolling of toner is significant.

When the fixing step is of a contact type, in particular, a heatpressure system, an elastic force possessed by paper used as a transfermaterial itself is utilized to some extent in order that a phenomenon inwhich the paper winds around a fixing unit in the fixing step may beprevented. That is, when toner used in development on the paper contactswith the fixing member of the fixing unit so as to melt, a force actingbetween the toner and the paper is larger than a force acting betweenthe fixing member and the toner, so the toner is peeled from the fixingmember by the elastic modulus of the paper, and a fixed image isobtained. Accordingly, when paper much thinner than a conventional oneand having a smaller elastic modulus than that of the conventional onesuch as paper for an advertisement folded in a newspaper is used as atransfer material, the elastic modulus of the paper is not sufficient,so a force acting between a fixing member and toner becomes larger thana force acting between the toner and the paper, and a phenomenon inwhich the toner and the paper wind around the fixing member is apt tooccur.

In the image-forming method of the present invention, when the truedensity of the cyan toner is represented by β_(TC) and a toner amountupon development of image data based on the CIELAB color coordinatesystem with (L*=53.9, a*=−37.0, b*=−50.1) (cyan solid image specified asa Japan color) onto the transfer material is represented by M1_(C)(mg/cm²), a coloring coefficient A_(C) represented by the followingexpression 9 is preferably 3.0 to 12.0.A _(C) =A _(C620)/(M1_(C)×ρ_(TC))  (Ex. 9)

The above coloring coefficient A_(C) is considered to show such coloringproperties for the image-forming method as described below: the extentof color development property possessed by toner to be used and theamount in which the toner is used in the formation of an image.According to the investigation conducted by the inventors of the presentinvention, as A_(C620) showing the color development property of thetoner increases, the amount of the toner to be used in the formation ofthe image is preferably reduced, so the larger A_(C), the bettercoloring efficiency the image-forming method shows. When A_(C) is lessthan 3.0, the color development property possessed by the toner is sosmall as compared to the amount of the toner to be used in thedevelopment of the image that the image density of the image may beinsufficient. In addition, even when the image density is sufficient,the amount of the toner to be used in the development is so large thatthe resolution of the image may reduce. On the other hand, when A_(C)exceeds 12.0, the color development property possessed by the toner isexcessively large, so, even when the resolution of the image issufficient, the color development efficiency of the colorant of thetoner reduces, and a representable color space narrows in some cases. Inaddition, even when the color space is sufficient, the amount of thetoner to be used in the formation of the image is so small that thecoarseness of a highlight portion, the disturbance of an edge portion ofa line image, or the like is apt to be remarkable. Accordingly, therange of A_(C) is more preferably 3.0 to 11.0, still more preferably 4.0to 11.0, or particularly preferably 6.0 to 11.0.

The cyan toner of the present invention has A_(C620) in a specificrange, and has color development property higher than that of anordinary toner. As a result, even when an image is formed in a statewhere a toner usage is small, specifically, A_(C) is 3.0 to 12.0, animage density and an image color gamut each of which is comparable to aconventional one can be achieved. However, when one attempts to reduce atoner consumption by reducing the thickness of a toner layer of whichthe image is formed, the toner penetrates into paper, so a fiber of thepaper is apt to be remarkable in an image portion. Alternatively, theappearance of the image is apt to reduce owing to a phenomenon such as areduction in image chroma. When an image is formed while a toner amounton paper is reduced, the amount of a binder resin of which the image isconstituted also reduces, so cold offset and hot offset are particularlyapt to occur. In view of the foregoing, the toner of the presentinvention, which is excellent in low-temperature fixability to someextent, preferably retains an appropriate viscosity even at hightemperatures.

It is preferable that: the step of forming the toner images include astep of transporting the toners to a developing portion with a tonercarrying member and a step of developing the electrostatic images withthe toners in the developing portion; and a ratio (Q_(C)/A_(C620)) ofthe absolute value for the charge quantity (Q_(C)) (mC/kg) of the toneron the toner carrying member in the transporting step to A_(C620) is22.0 to 50.0. In the present invention, a cyan toner having specificreflection spectral characteristics and more excellent in colordevelopment property than a conventional toner is used, but a toneramount with which an electrostatic latent image is developed ispreferably controlled in consideration of a relationship between thecolor development property and the charge quantity possessed by thetoner. That is, the following procedure is preferably adopted: as longas Q_(C)/A_(C620) falls within the above range, as A_(C620) of the tonerto be used increases, the value for Q_(C) is increased so that a toneramount used in the development of image data is reduced. With suchprocedure, the color development efficiency of the toner can beadditionally improved, and the resolution of an image is improved. Inaddition, a toner excellent in color development property is apt to showa remarkable image failure even when the toner scatters to a slightextent, so the following procedure is preferably adopted: as the colordevelopment property of the toner becomes more excellent, the chargequantity of the toner is increased so that an image failure such astoner scattering is suppressed. Further, as the color developmentproperty of the toner becomes more excellent, the disturbance of an edgeportion of, for example, a dot image or line image is more liable to beremarkable. However, when the charge quantity of the toner is retainedin a certain range in association with the color development property ofthe toner, the disturbance of the edge portion is suppressed, and areduction in resolution of the image is easily suppressed. WhenQ_(C)/A_(C620) described above is less than 22.0, the charge quantity ofthe toner is so small as compared to the color development property ofthe toner that a toner amount to be used in the development of an imageincreases, and, even when the image density of the image is sufficient,the resolution of the image may reduce. Alternatively, the colordevelopment property of the toner is so large as compared to the chargequantity of the toner that, even when the image resolution issufficient, the color development efficiency of the colorant of thetoner reduces, and a representable color space narrows in some cases.When Q_(C)/A_(C620) described above exceeds 50.0, the charge quantity ofthe toner is so large as compared to the color development property ofthe toner that a toner amount to be used in the development of an imageis excessively small, and, even when the image density of the image issufficient, the coarseness of a highlight portion, the disturbance of anedge portion of a line image, or the like is apt to be remarkable.Alternatively, the color development property of the toner is so smallas compared to the charge quantity of the toner that, even when theimage resolution is sufficient, the image density or image color gamutof the image may be insufficient. Accordingly, Q_(C)/A_(C620) describedabove is more preferably 24.0 to 45.0, still more preferably 27.0 to44.6, or still more preferably 30.0 to 44.6.

In the image-forming method of the present invention, M1_(C) (mg/cm²)described above is preferably (0.10×ρ_(TC)) to (0.40×ρ_(TC)) mg/cm²because a toner consumption is reduced, and the effects of the presentinvention is favorably exerted. When M1_(C) is less than (0.10×ρ_(TC))mg/cm², the toner penetrates into paper, and the representable colorspace of an image narrows in some cases. Alternatively, the number oftoner particles of which the image is formed reduces, and the uniformityof the image reduces in some cases. When M1_(C) exceeds (0.40×ρ_(TC))mg/cm², the resolution of the image is apt to reduce. In addition, whena transfer material having a small elastic modulus is used, the windingof paper as the transfer material in the fixing step is apt to occur.Accordingly, the above range of M1_(C) is more preferably (0.12×ρ_(TC))to (0.35×ρ_(TC)) mg/cm², or particularly preferably (0.15×ρ_(TC)) to(0.30×ρ_(TC)) mg/cm².

In the step of forming the toner images, a ratio (H_(C80)/H_(C20)) ofthe average height (H_(C80)) of the toner layer of a toner image formedon the electrostatic image bearing member for image data having a cyanmonochromatic density of 80% to the average height (H_(C20)) of thetoner layer of a toner image formed on the electrostatic image bearingmember for image data having a cyan monochromatic density of 20% ispreferably 0.90 to 1.30. According to the present invention, anadditional improving effect on an image resolution is obtained, glossnon-uniformity is suppressed, an image with suppressed surfaceunevenness is obtained irrespective of the thickness of the transfermaterial, and a toner consumption can be reduced. When a toner excellentin color development property is used like the present invention, thetinge of an image at a certain point of the image is largely changed bythe number of toner particles present in the direction perpendicular toan image surface at the point. Accordingly, in the present invention,such image-forming method as described below is preferably employed: thenumbers of toner particles present in the directions perpendicular tothe surfaces of the respective gradation images are uniformized to theextent possible irrespective of the image densities of the images. WhenH_(C80)/H_(C20) described above is less than 0.90 or exceeds 1.30, arange from the highlight portion to halftone portion of an image becomessusceptible to image non-uniformity caused by changing in tinges owingto the non-uniformity of the number of toner particles present in thedirection perpendicular to the surface of the image. In particular, whenH_(C80)/H_(C20) exceeds 1.30, the resolution of a high-density gradationportion is apt to reduce, and the reproducibility of an image for imagedata is apt to reduce. Accordingly, H_(C80)/H_(C20) described above ispreferably 0.95 to 1.20, or particularly preferably 1.00 to 1.15. Suchimage formation is effective in an image-forming method in which imageformation based on an area coverage modulation method where gradation isrepresented on the basis of the area of an image region is adopted overa range from a low-density region to a high-density solid image region.

The present invention relates to a full-color image-forming methodincluding the steps of: forming electrostatic images on a chargedelectrostatic image bearing member; developing the formed electrostaticimages with toners to form toner images; transferring the formed tonerimages onto a transfer material; and fixing the transferred toner imagesto the transfer material to form fixed images, in which: the step offorming the toner images includes a step of performing development witha first toner selected from a black toner, a cyan toner, a magentatoner, and a yellow toner to form a first toner image, a step ofperforming development with a second toner except the first tonerselected from the black toner, the cyan toner, the magenta toner, andthe yellow toner to form a second toner image, a step of performingdevelopment with a third toner except the first toner and the secondtoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a third toner image, and a step ofperforming development with a fourth toner except the first toner, thesecond toner, and the third toner selected from the black toner, thecyan toner, the magenta toner, and the yellow toner to form a fourthtoner image; and the magenta toner is a magenta toner containing atleast a binder resin and a colorant, and the magenta toner has a value(h*_(M)) for a hue angle h* based on a CIELAB color coordinate system of330.0 to 30.0, an absorbance (A_(M570)) at a wavelength of 570 nm of1.550 or more, an absorbance (A_(M620)) at a wavelength of 620 nm of0.250 or less, and a ratio (A_(M570)/A_(M450)) of A_(M570) to anabsorbance (A_(M450)) at a wavelength of 450 nm of 1.80 to 3.50 inreflectance spectrophotometry.

According to such full-color image-forming method, an image color gamutcomparable to or better than a conventional one can be represented, agood-appearance image with reduced surface unevenness can be obtained,and a running cost can be suppressed as a result of a reduction inconsumption of the magenta toner. Further, a toner amount to be used inthe development of the toner images on the electrostatic image bearingmember can be reduced, so toner scattering in the transferring step canbe suppressed, and toner images faithful to the electrostatic images canbe formed on the transfer material. The deformation of each of the tonerimages on the transfer material is suppressed in the transferring step,so fixed images faithful to the electrostatic images can be formed. Inaddition, a toner amount on a transfer material can be reduced, so, evenwhen paper much thinner than a conventional one such as paper for anadvertisement folded in a newspaper is used as a transfer material, afixation failure or the winding of the paper around a fixing unit issuppressed, and an image with small surface unevenness can be formed.

The reason for the foregoing is as described below. Since a magentatoner having specific reflection spectral characteristics and moreexcellent in color development property than a conventional toner isused, a toner amount per unit area needed for representing an imagecolor gamut and a color space each of which is comparable to or betterthan a conventional one for certain image data can be reduced ascompared to a conventional magenta toner. As a result, the amount of themagenta toner to be used in the development of certain image data on aunit area of the electrostatic image bearing member can be reduced. Thetoner amount per unit area is small, but the area of an electrostaticimage to be formed on the electrostatic image bearing member isconstant, so the height of a toner image developed on the electrostaticimage bearing member with the toner can be reduced. According to theinvestigation conducted by the inventors of the present invention, theheight of a toner image on the electrostatic image bearing member andthe ease with which a toner scatters in the transferring step establisha proportional relationship. Accordingly, reducing the above height ofthe toner image suppresses the scattering of the toner, and allows thetoner image on the electrostatic image bearing member to be transferredonto the transfer material with additional faithfulness. The effect ismore significant in the case of an image-forming method involving theuse of an intermediate transfer body, and is particularly significantwhen the intermediate transfer body is used twice or more.

In general, a toner image transferred onto a transfer material undergoesa fixing step so that a fixed image is formed. According to theinvestigation conducted by the inventors of the present invention, theheight of an unfixed toner image on the transfer material and the easewith which the toner image spreads in a transferring step establish aproportional relationship. That is, even if a high-definition,high-resolution toner image is formed on the transfer material, when thetoner image has a high height, the resolution of a fixed image reducesowing to the melt spread or rolling of toner in the fixing step. In thefull-color image-forming method of the present invention, the height ofa magenta toner image on the transfer material can be reduced, so aphenomenon such as the melt spread or rolling of toner in the fixingstep is suppressed, and hence a fixed toner image faithful to theunfixed toner image on the transfer material can be formed.

Those effects are exerted irrespective of whether the fixing step is ofa contact type or a non-contact type. When the fixing step is based on aheat fixing system, those effects are particularly significant; in thecase of a fixing step based on a heat pressure system, a suppressingeffect on the rolling of toner is significant.

When the fixing step is of a contact type, in particular, a heatpressure system, an elastic force possessed by paper used as a transfermaterial itself is utilized to some extent in order that a phenomenon inwhich the paper winds around a fixing unit in the fixing step may beprevented. That is, when toner used in development on the paper contactswith the fixing member of the fixing unit so as to melt, a force actingbetween the toner and the paper is larger than a force acting betweenthe fixing member and the toner, so the toner is peeled from the fixingmember by the elastic modulus of the paper, and a fixed image isobtained. Accordingly, when paper much thinner than a conventional oneand having a smaller elastic modulus than that of the conventional onesuch as paper for an advertisement folded in a newspaper is used as atransfer material, the elastic modulus of the paper is not sufficient,so a force acting between a fixing member and toner becomes larger thana force acting between the toner and the paper, and a phenomenon inwhich the toner and the paper wind around the fixing member is apt tooccur.

In the image-forming method of the present invention, when the truedensity of the magenta toner is represented by ρ_(TM) and a toner amountupon development of image data based on the CIELAB color coordinatesystem with (L*=47.0, a*=75.0, b*=−6.0) (magenta solid image specifiedas a Japan color) onto the transfer material is represented by M1_(M)(mg/cm²), a coloring coefficient A_(M) represented by the followingexpression 10 is preferably 3.0 to 12.0.A _(M) =A _(M570)/(M1_(M)×ρ_(TM))  (Ex. 10)

The above coloring coefficient A_(M) is considered to show such coloringproperties for the image-forming method as described below: the extentof color development property possessed by toner to be used and theamount in which the toner is used in the formation of an image.According to the investigation conducted by the inventors of the presentinvention, as A_(M570) showing the color development property of thetoner increases, the amount of the toner to be used in the formation ofthe image is preferably reduced, so the larger A_(M), the bettercoloring efficiency the image-forming method shows. When A_(M) is lessthan 3.0, the color development property possessed by the toner is sosmall that the image density of the image may be insufficient. Inaddition, even when the image density is sufficient, the amount of thetoner to be used in the development is so large that the resolution ofthe image may reduce. On the other hand, when A_(M) exceeds 12.0, thecolor development property possessed by the toner is excessively large,so, even when the resolution of the image is sufficient, the colordevelopment efficiency of the colorant of the toner reduces, and arepresentable color space narrows in some cases. In addition, even whenthe color space is sufficient, the amount of the toner to be used in theformation of the image is so small that the coarseness of a highlightportion, the disturbance of an edge portion of a line image, or the likeis apt to be remarkable. Accordingly, the range of A_(M) is morepreferably 3.0 to 11.0, still more preferably 4.0 to 11.0, orparticularly preferably 6.0 to 11.0.

The magenta toner of the present invention has A_(M570) in a specificrange, and has color development property higher than that of anordinary toner. As a result, even when an image is formed in a statewhere a toner usage is small, specifically, A_(M) is 3.0 to 12.0, animage density and an image color gamut each of which is comparable to aconventional one can be achieved. However, when one attempts to reduce atoner consumption by reducing the thickness of a toner layer of whichthe image is formed, the toner penetrates into paper, so a fiber of thepaper is apt to be remarkable in an image portion. Alternatively, theappearance of the image is apt to reduce owing to a phenomenon such as areduction in image chroma. When an image is formed while a toner amounton paper is reduced, the amount of a binder resin of which the image isconstituted also reduces, so cold offset and hot offset are particularlyapt to occur. In view of the foregoing, the toner of the presentinvention, which is excellent in low-temperature fixability to someextent, preferably retains an appropriate viscosity even at hightemperatures.

It is preferable that: the step of forming the toner images include astep of transporting the toners to a developing portion with a tonercarrying member and a step of developing the electrostatic images withthe toners in the developing portion; and a ratio (Q_(M)/A_(M570)) ofthe absolute value for the charge quantity (Q_(M)) (mC/kg) of the toneron the toner carrying member in the transporting step to A_(M570) is22.0 to 50.0. In the present invention, a magenta toner having specificreflection spectral characteristics and more excellent in colordevelopment property than a conventional toner is used, but a toneramount with which an electrostatic latent image is developed ispreferably controlled in consideration of a relationship between thecolor development property and the charge quantity possessed by thetoner. That is, the following procedure is preferably adopted: as longas Q_(M)/A_(M570) falls within the above range, as A_(M570) of the tonerto be used increases, the value for Q_(M) is increased so that a toneramount used in the development of image data is reduced. With suchprocedure, the color development efficiency of the toner can beadditionally improved, and the resolution of an image is improved. Inaddition, a toner excellent in color development property is apt to showa remarkable image failure even when the toner scatters to a slightextent, so the following procedure is preferably adopted: as the colordevelopment property of the toner becomes more excellent, the chargequantity of the toner is increased so that an image failure such astoner scattering is suppressed. Further, as the color developmentproperty of the toner becomes more excellent, the disturbance of an edgeportion of, for example, a dot image or line image is more liable to beremarkable. However, when the charge quantity of the toner is retainedin a certain range in association with the color development property ofthe toner, the disturbance of the edge portion is suppressed, and areduction in resolution of the image is easily suppressed. WhenQ_(M)/A_(M570) described above is less than 22.0, the charge quantity ofthe toner is so small as compared to the color development property ofthe toner that a toner amount to be used in the development of an imageincreases, and, even when the image density of the image is sufficient,the resolution of the image may reduce. Alternatively, the colordevelopment property of the toner is so large as compared to the chargequantity of the toner that, even when the image resolution issufficient, the color development efficiency of the colorant of thetoner reduces, and a representable color space narrows in some cases.When Q_(M)/A_(M570) described above exceeds 50.0, the charge quantity ofthe toner is so large as compared to the color development property ofthe toner that a toner amount to be used in the development of an imageis excessively small, and, even when the image density of the image issufficient, the coarseness of a highlight portion, the disturbance of anedge portion of a line image, or the like is apt to be remarkable.Alternatively, the color development property of the toner is so smallas compared to the charge quantity of the toner that, even when theimage resolution is sufficient, the image density or image color gamutof the image may be insufficient. Accordingly, Q_(M)/A_(M570) describedabove is more preferably 23.0 to 45.0, still more preferably 26.0 to44.0, or still more preferably 30.0 to 44.6.

In the image-forming method of the present invention, M1_(M) (mg/cm²)described above is preferably (0.10×ρ_(TM)) to (0.40×ρ_(TM)) mg/cm²because a toner consumption is reduced, and the effects of the presentinvention is favorably exerted. When M1_(M) is less than (0.10×ρ_(TM))mg/cm², the toner penetrates into paper, and the representable colorspace of an image narrows in some cases. Alternatively, the number oftoner particles of which the image is formed reduces, and the uniformityof the image reduces in some cases. When M1_(M) exceeds (0.40×ρ_(TM))mg/cm², the resolution of the image is apt to reduce. In addition, whena transfer material having a small elastic modulus is used, the windingof paper as the transfer material in the fixing step is apt to occur.Accordingly, the above range of M1_(M) is more preferably (0.12×ρ_(TM))to (0.35×ρ_(TM)) mg/cm², or particularly preferably (0.15×ρ_(TM)) to(0.30×ρ_(TM)) mg/cm².

In the step of forming the toner images, a ratio (H_(M80)/H_(M20)) ofthe average height (H_(M80)) of the toner layer of a toner image formedon the electrostatic image bearing member for image data having amagenta monochromatic density of 80% to the average height (H_(M20)) ofthe toner layer of a toner image formed on the electrostatic imagebearing member for image data having a magenta monochromatic density of20% is preferably 0.90 to 1.30. According to the present invention, anadditional improving effect on an image resolution is obtained, glossnon-uniformity is suppressed, an image with suppressed surfaceunevenness is obtained irrespective of the thickness of the transfermaterial, and a toner consumption can be reduced. When a toner excellentin color development property is used like the present invention, thetinge of an image at a certain point of the image is largely changed bythe number of toner particles present in the direction perpendicular toan image surface at the point. Accordingly, in the present invention,such image-forming method as described below is preferably employed: thenumbers of toner particles present in the directions perpendicular tothe surfaces of the respective gradation images are uniformized to theextent possible irrespective of the image densities of the images. WhenH_(M80)/H_(M20) described above is less than 0.90 or exceeds 1.30, arange from the highlight portion to halftone portion of an image becomessusceptible to image non-uniformity caused by changing in tinges owingto the non-uniformity of the number of toner particles present in thedirection perpendicular to the surface of the image. In particular, whenH_(M80)/H_(M20) exceeds 1.30, the resolution of a high-density gradationportion is apt to reduce, and the reproducibility of an image for imagedata is apt to reduce. Accordingly, H_(M80)/H_(M20) described above ispreferably 0.95 to 1.20, or particularly preferably 1.00 to 1.15. Suchimage formation is effective in an image-forming method in which imageformation based on an area coverage modulation method where gradation isrepresented on the basis of the area of an image region is adopted overa range from a low-density region to a high-density solid image region.

The present invention relates to a full-color image-forming methodincluding the steps of: forming electrostatic images on a chargedelectrostatic image bearing member; developing the formed electrostaticimages with toners to form toner images; transferring the formed tonerimages onto a transfer material; and fixing the transferred toner imagesto the transfer material to form fixed images, in which: the step offorming the toner images includes a step of performing development witha first toner selected from a black toner, a cyan toner, a magentatoner, and a yellow toner to form a first toner image, a step ofperforming development with a second toner except the first tonerselected from the black toner, the cyan toner, the magenta toner, andthe yellow toner to form a second toner image, a step of performingdevelopment with a third toner except the first toner and the secondtoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a third toner image, and a step ofperforming development with a fourth toner except the first toner, thesecond toner, and the third toner selected from the black toner, thecyan toner, the magenta toner, and the yellow toner to form a fourthtoner image; and the yellow toner is a yellow toner containing at leasta binder resin and a colorant, and the yellow toner has a value (h*_(Y))for a hue angle h* based on a CIELAB color coordinate system of 75.0 to120.0, an absorbance (A_(Y450)) at a wavelength of 450 nm of 1.600 ormore, an absorbance (A_(Y470)) at a wavelength of 470 nm of 1.460 ormore, and a an absorbance (A_(Y510)) at a wavelength of 510 nm of 0.500or less in reflectance spectrophotometry.

According to such full-color image-forming method, an image color gamutcomparable to or better than a conventional one can be represented, agood-appearance image with reduced surface unevenness can be obtained,and a running cost can be suppressed as a result of a reduction inconsumption of the yellow toner. Further, a toner amount to be used inthe development of the toner images on the electrostatic image bearingmember can be reduced, so toner scattering in the transferring step canbe suppressed, and toner images faithful to the electrostatic images canbe formed on the transfer material. The deformation of each of the tonerimages on the transfer material is suppressed in the transferring step,so fixed images faithful to the electrostatic images can be formed. Inaddition, a toner amount on a transfer material can be reduced, so, evenwhen paper much thinner than a conventional one such as paper for anadvertisement folded in a newspaper is used as a transfer material, afixation failure or the winding of the paper around a fixing unit issuppressed, and an image with small surface unevenness can be formed.

The reason for the foregoing is as described below. Since a yellow tonerhaving specific reflection spectral characteristics and more excellentin color development property than a conventional toner is used, a toneramount per unit area needed for representing an image color gamut and acolor space each of which is comparable to or better than a conventionalone for certain image data can be reduced as compared to a conventionalyellow toner. As a result, the amount of the yellow toner to be used inthe development of certain image data on a unit area of theelectrostatic image bearing member can be reduced. The toner amount perunit area is small, but the area of an electrostatic image to be formedon the electrostatic image bearing member is constant, so the height ofa toner image developed on the electrostatic image bearing member withthe toner can be reduced. According to the investigation conducted bythe inventors of the present invention, the height of a toner image onthe electrostatic image bearing member and the ease with which a tonerscatters in the transferring step establish a proportional relationship.Accordingly, reducing the above height of the toner image suppresses thescattering of the toner, and allows the toner image on the electrostaticimage bearing member to be transferred onto the transfer material withadditional faithfulness. The effect is more significant in the case ofan image-forming method involving the use of an intermediate transferbody, and is particularly significant when the intermediate transferbody is used twice or more.

In general, a toner image transferred onto a transfer material undergoesa fixing step so that a fixed image is formed. According to theinvestigation conducted by the inventors of the present invention, theheight of an unfixed toner image on the transfer material and the easewith which the toner image spreads in a transferring step establish aproportional relationship. That is, even if a high-definition,high-resolution toner image is formed on the transfer material, when thetoner image has a high height, the resolution of a fixed image reducesowing to the melt spread or rolling of toner in the fixing step. In thefull-color image-forming method of the present invention, the height ofa yellow toner image on the transfer material can be reduced, so aphenomenon such as the melt spread or rolling of toner in the fixingstep is suppressed, and hence a fixed toner image faithful to theunfixed toner image on the transfer material can be formed.

Those effects are exerted irrespective of whether the fixing step is ofa contact type or a non-contact type. When the fixing step is based on aheat fixing system, those effects are particularly significant; in thecase of a fixing step based on a heat pressure system, a suppressingeffect on the rolling of toner is significant.

When the fixing step is of a contact type, in particular, a heatpressure system, an elastic force possessed by paper used as a transfermaterial itself is utilized to some extent in order that a phenomenon inwhich the paper winds around a fixing unit in the fixing step may beprevented. That is, when toner used in development on the paper contactswith the fixing member of the fixing unit so as to melt, a force actingbetween the toner and the paper is larger than a force acting betweenthe fixing member and the toner, so the toner is peeled from the fixingmember by the elastic modulus of the paper, and a fixed image isobtained. Accordingly, when paper much thinner than a conventional oneand having a smaller elastic modulus than that of the conventional onesuch as paper for an advertisement folded in a newspaper is used as atransfer material, the elastic modulus of the paper is not sufficient,so a force acting between a fixing member and toner becomes larger thana force acting between the toner and the paper, and a phenomenon inwhich the toner and the paper wind around the fixing member is apt tooccur.

In the image-forming method of the present invention, when the truedensity of the yellow toner is represented by ρ_(TY) and a toner amountupon development of image data based on the CIELAB color coordinatesystem with (L*=88.0, a*=−6.0, b*=95.0) (yellow solid image specified asa Japan color) onto the transfer material is represented by M1_(Y)(mg/cm²), a coloring coefficient A_(Y) represented by the followingexpression 11 is preferably 3.0 to 12.0.A _(Y) =A _(Y450)/(M1_(Y)×ρ_(TY))  (Ex. 11)

The above coloring coefficient A_(Y) is considered to show such coloringproperties for the image-forming method as described below: the extentof color development property possessed by toner to be used and theamount in which the toner is used in the formation of an image.According to the investigation conducted by the inventors of the presentinvention, as A_(Y450) showing the color development property of thetoner increases, the amount of the toner to be used in the formation ofthe image is preferably reduced, so the larger A_(Y), the bettercoloring efficiency the image-forming method shows. When A_(Y) is lessthan 3.0, the color development property possessed by the toner is sosmall as compared to the amount of the toner to be used in thedevelopment of the image that the image density of the image may beinsufficient. In addition, even when the image density is sufficient,the amount of the toner to be used in the development is so large thatthe resolution of the image may reduce. On the other hand, when A_(Y)exceeds 12.0, the color development property possessed by the toner isexcessively large, so, even when the resolution of the image issufficient, the color development efficiency of the colorant of thetoner reduces, and a representable color space narrows in some cases. Inaddition, even when the color space is sufficient, the amount of thetoner to be used in the formation of the image is so small that thecoarseness of a highlight portion, the disturbance of an edge portion ofa line image, or the like is apt to be remarkable. Accordingly, therange of A_(Y) is more preferably 3.0 to 11.0, still more preferably 4.0to 11.0, or particularly preferably 6.0 to 11.0.

The yellow toner of the present invention has A_(Y450) in a specificrange, and has color development property higher than that of anordinary toner. As a result, even when an image is formed in a statewhere a toner usage is small, specifically, A_(Y) is 3.0 to 12.0, animage density and an image color gamut each of which is comparable to aconventional one can be achieved. However, when one attempts to reduce atoner consumption by reducing the thickness of a toner layer of whichthe image is formed, the toner penetrates into paper, so a fiber of thepaper is apt to be remarkable in an image portion. Alternatively, theappearance of the image is apt to reduce owing to a phenomenon such as areduction in image chroma. When an image is formed while a toner amounton paper is reduced, the amount of a binder resin of which the image isconstituted also reduces, so cold offset and hot offset are particularlyapt to occur. In view of the foregoing, the toner of the presentinvention, which is excellent in low-temperature fixability to someextent, preferably retains an appropriate viscosity even at hightemperatures.

It is preferable that: the step of forming the toner images include astep of transporting the toners to a developing portion with a tonercarrying member and a step of developing the electrostatic images withthe toners in the developing portion; and a ratio (Q_(Y)/A_(Y450)) ofthe absolute value for the charge quantity (Q_(Y)) (mC/kg) of the toneron the toner carrying member in the transporting step to A_(Y450) is22.0 to 50.0. In the present invention, a yellow toner having specificreflection spectral characteristics and more excellent in colordevelopment property than a conventional toner is used, but a toneramount with which an electrostatic latent image is developed ispreferably controlled in consideration of a relationship between thecolor development property and the charge quantity possessed by thetoner. That is, the following procedure is preferably adopted: as longas Q_(Y)/A_(Y450) falls within the above range, as A_(Y450) of the tonerto be used increases, the value for Q_(Y) is increased so that a toneramount used in the development of image data is reduced. With suchprocedure, the color development efficiency of the toner can beadditionally improved, and the resolution of an image is improved. Inaddition, a toner excellent in color development property is apt to showa remarkable image failure even when the toner scatters to a slightextent, so the following procedure is preferably adopted: as the colordevelopment property of the toner becomes more excellent, the chargequantity of the toner is increased so that an image failure such astoner scattering is suppressed. Further, as the color developmentproperty of the toner becomes more excellent, the disturbance of an edgeportion of, for example, a dot image or line image is more liable to beremarkable. However, when the charge quantity of the toner is retainedin a certain range in association with the color development property ofthe toner, the disturbance of the edge portion is suppressed, and areduction in resolution of the image is easily suppressed. WhenQ_(Y)/A_(Y450) described above is less than 22.0, the charge quantity ofthe toner is so small as compared to the color development property ofthe toner that a toner amount to be used in the development of an imageincreases, and, even when the image density of the image is sufficient,the resolution of the image may reduce. Alternatively, the colordevelopment property of the toner is so large as compared to the chargequantity of the toner that, even when the image resolution issufficient, the color development efficiency of the colorant of thetoner reduces, and a representable color space narrows in some cases.When Q_(Y)/A_(Y450) described above exceeds 50.0, the charge quantity ofthe toner is so large as compared to the color development property ofthe toner that a toner amount to be used in the development of an imageis excessively small, and, even when the image density of the image issufficient, the coarseness of a highlight portion, the disturbance of anedge portion of a line image, or the like is apt to be remarkable.Alternatively, the color development property of the toner is so smallas compared to the charge quantity of the toner that, even when theimage resolution is sufficient, the image density or image color gamutof the image may be insufficient. Accordingly, Q_(Y)/A_(Y450) describedabove is more preferably 23.0 to 45.0, still more preferably 27.0 to45.0, or still more preferably 30.0 to 45.0.

In the image-forming method of the present invention, M1_(Y) (mg/cm²)described above is preferably (0.10×ρ_(TY)) to (0.40×ρ_(TY)) mg/cm²because a toner consumption is reduced, and the effects of the presentinvention is favorably exerted. When M1_(Y) is less than (0.10×ρ_(TY))mg/cm², the toner penetrates into paper, and the representable colorspace of an image narrows in some cases. Alternatively, the number oftoner particles of which the image is formed reduces, and the uniformityof the image reduces in some cases. When M1_(Y) exceeds (0.40×ρ_(TY))mg/cm², the resolution of the image is apt to reduce. In addition, whena transfer material having a small elastic modulus is used, the windingof paper as the transfer material in the fixing step is apt to occur.Accordingly, the above range of M1_(Y) is more preferably (0.12×ρ_(TY))to (0.35×ρ_(TY)) mg/cm², or particularly preferably (0.15×ρ_(TY)) to(0.30×ρ_(TY)) mg/cm².

In the step of forming the toner images, a ratio (H_(Y80)/H_(Y20)) ofthe average height (H_(Y80)) of the toner layer of a toner image formedon the electrostatic image bearing member for image data having a yellowmonochromatic density of 80% to the average height (H_(Y20)) of thetoner layer of a toner image formed on the electrostatic image bearingmember for image data having a yellow monochromatic density of 20% ispreferably 0.90 to 1.30. According to the present invention, anadditional improving effect on an image resolution is obtained, glossnon-uniformity is suppressed, an image with suppressed surfaceunevenness is obtained irrespective of the thickness of the transfermaterial, and a toner consumption can be reduced. When a toner excellentin color development property is used like the present invention, thetinge of an image at a certain point of the image is largely changed bythe number of toner particles present in the direction perpendicular toan image surface at the point. Accordingly, in the present invention,such image-forming method as described below is preferably employed: thenumbers of toner particles present in the directions perpendicular tothe surfaces of the respective gradation images are uniformized to theextent possible irrespective of the image densities of the images. WhenH_(Y80)/H_(Y20) described above is less than 0.90 or exceeds 1.30, arange from the highlight portion to halftone portion of an image becomessusceptible to image non-uniformity caused by changing in tinges owingto the non-uniformity of the number of toner particles present in thedirection perpendicular to the surface of the image. In particular, whenH_(Y80)/H_(Y20) exceeds 1.30, the resolution of a high-density gradationportion is apt to reduce, and the reproducibility of an image for imagedata is apt to reduce. Accordingly, H_(Y80)/H_(Y20) described above ispreferably 0.95 to 1.20, or particularly preferably 1.00 to 1.15. Suchimage formation is effective in an image-forming method in which imageformation based on an area coverage modulation method where gradation isrepresented on the basis of the area of an image region is adopted overa range from a low-density region to a high-density solid image region.

The present invention relates to a full-color image-forming methodincluding the steps of: forming electrostatic images on a chargedelectrostatic image bearing member; developing the formed electrostaticimages with toners to form toner images; transferring the formed tonerimages onto a transfer material; and fixing the transferred toner imagesto the transfer material to form fixed images, in which: the step offorming the toner images includes a step of performing development witha first toner selected from a black toner, a cyan toner, a magentatoner, and a yellow toner to form a first toner image, a step ofperforming development with a second toner except the first tonerselected from the black toner, the cyan toner, the magenta toner, andthe yellow toner to form a second toner image, a step of performingdevelopment with a third toner except the first toner and the secondtoner selected from the black toner, the cyan toner, the magenta toner,and the yellow toner to form a third toner image, and a step ofperforming development with a fourth toner except the first toner, thesecond toner, and the third toner selected from the black toner, thecyan toner, the magenta toner, and the yellow toner to form a fourthtoner image; and the black toner is a black toner containing at least abinder resin and a colorant, and the black toner has a value (c*_(K))for c* based on a CIELAB color coordinate system of 20.0 or less, anabsorbance (A_(K600)) at a wavelength of 600 nm of 1.610 or more, and aratio (A_(K600)/A_(K460)) of A_(K600) to an absorbance (A_(K460)) at awavelength of 460 nm of 0.970 to 1.035 in reflectance spectrophotometry.

According to such full-color image-forming method, an image color gamutcomparable to or better than a conventional one can be represented, agood-appearance image with reduced surface unevenness can be obtained,and a running cost can be suppressed as a result of a reduction inconsumption of the black toner. Further, a toner amount to be used inthe development of the toner images on the electrostatic image bearingmember can be reduced, so toner scattering in the transferring step canbe suppressed, and toner images faithful to the electrostatic images canbe formed on the transfer material. The deformation of each of the tonerimages on the transfer material is suppressed in the transferring step,so fixed images faithful to the electrostatic images can be formed. Inaddition, a toner amount on a transfer material can be reduced, so, evenwhen paper much thinner than a conventional one such as paper for anadvertisement folded in a newspaper is used as a transfer material, afixation failure or the winding of the paper around a fixing unit issuppressed, and an image with small surface unevenness can be formed.

The reason for the foregoing is as described below. Since a black tonerhaving specific reflection spectral characteristics and more excellentin color development property than a conventional toner is used, a toneramount per unit area needed for representing an image color gamut and acolor space each of which is comparable to or better than a conventionalone for certain image data can be reduced as compared to a conventionalblack toner. As a result, the amount of the black toner to be used inthe development of certain image data on a unit area of theelectrostatic image bearing member can be reduced. The toner amount perunit area is small, but the area of an electrostatic image to be formedon the electrostatic image bearing member is constant, so the height ofa toner image developed on the electrostatic image bearing member withthe toner can be reduced. According to the investigation conducted bythe inventors of the present invention, the height of a toner image onthe electrostatic image bearing member and the ease with which a tonerscatters in the transferring step establish a proportional relationship.Accordingly, reducing the above height of the toner image suppresses thescattering of the toner, and allows the toner image on the electrostaticimage bearing member to be transferred onto the transfer material withadditional faithfulness. The effect is more significant in the case ofan image-forming method involving the use of an intermediate transferbody, and is particularly significant when the intermediate transferbody is used twice or more.

In general, a toner image transferred onto a transfer material undergoesa fixing step so that a fixed image is formed. According to theinvestigation conducted by the inventors of the present invention, theheight of an unfixed toner image on the transfer material and the easewith which the toner image spreads in a transferring step establish aproportional relationship. That is, even if a high-definition,high-resolution toner image is formed on the transfer material, when thetoner image has a high height, the resolution of a fixed image reducesowing to the melt spread or rolling of toner in the fixing step. In thefull-color image-forming method of the present invention, the height ofa black toner image on the transfer material can be reduced, so aphenomenon such as the melt spread or rolling of toner in the fixingstep is suppressed, and hence a fixed toner image faithful to theunfixed toner image on the transfer material can be formed.

Those effects are exerted irrespective of whether the fixing step is ofa contact type or a non-contact type. When the fixing step is based on aheat fixing system, those effects are particularly significant; in thecase of a fixing step based on a heat pressure system, a suppressingeffect on the rolling of toner is significant.

When the fixing step is of a contact type, in particular, a heatpressure system, an elastic force possessed by paper used as a transfermaterial itself is utilized to some extent in order that a phenomenon inwhich the paper winds around a fixing unit in the fixing step may beprevented. That is, when toner used in development on the paper contactswith the fixing member of the fixing unit so as to melt, a force actingbetween the toner and the paper is larger than a force acting betweenthe fixing member and the toner, so the toner is peeled from the fixingmember by the elastic modulus of the paper, and a fixed image isobtained. Accordingly, when paper much thinner than a conventional oneand having a smaller elastic modulus than that of the conventional onesuch as paper for an advertisement folded in a newspaper is used as atransfer material, the elastic modulus of the paper is not sufficient,so a force acting between a fixing member and toner becomes larger thana force acting between the toner and the paper, and a phenomenon inwhich the toner and the paper wind around the fixing member is apt tooccur.

In the image-forming method of the present invention, when the truedensity of the black toner is represented by ρ_(TK) and a toner amountupon development of image data based on the CIELAB color coordinatesystem with (L*=13.2, a*=1.3, b*=1.9) (black solid image specified as a

Japan color) onto the transfer material is represented by M1_(K)(mg/cm²), a coloring coefficient A_(K) represented by the followingexpression 12 is preferably 3.0 to 12.0.A _(K) =A _(K600)/(M1_(K)×ρ_(TK))  (Ex. 12)

The above coloring coefficient A_(K) is considered to show such coloringproperties for the image-forming method as described below: the extentof color development property possessed by toner to be used and theamount in which the toner is used in the formation of an image.According to the investigation conducted by the inventors of the presentinvention, as A_(K600) showing the color development property of thetoner increases, the amount of the toner to be used in the formation ofthe image is preferably reduced, so the larger A_(K), the bettercoloring efficiency the image-forming method shows. When A_(K) is lessthan 3.0, the color development property possessed by the toner is sosmall as compared to the amount of the toner to be used in thedevelopment of the image that the image density of the image may beinsufficient. In addition, even when the image density is sufficient,the amount of the toner to be used in the development is so large thatthe resolution of the image may reduce. On the other hand, when A_(K)exceeds 12.0, the color development property possessed by the toner isexcessively large, so, even when the resolution of the image issufficient, the color development efficiency of the colorant of thetoner reduces, and a representable color space narrows in some cases. Inaddition, even when the color space is sufficient, the amount of thetoner to be used in the formation of the image is so small that thecoarseness of a highlight portion, the disturbance of an edge portion ofa line image, or the like is apt to be remarkable. Accordingly, therange of A_(K) is more preferably 3.0 to 11.0, still more preferably 4.0to 11.0, or particularly preferably 6.0 to 11.0.

The black toner of the present invention has A_(K600) in a specificrange, and has color development property higher than that of anordinary toner. As a result, even when an image is formed in a statewhere a toner usage is small, specifically, A_(K) is 3.0 to 12.0, animage density and an image color gamut each of which is comparable to aconventional one can be achieved. However, when one attempts to reduce atoner consumption by reducing the thickness of a toner layer of whichthe image is formed, the toner penetrates into paper, so a fiber of thepaper is apt to be remarkable in an image portion. Alternatively, theappearance of the image is apt to reduce owing to a phenomenon such as areduction in image chroma. When an image is formed while a toner amounton paper is reduced, the amount of a binder resin of which the image isconstituted also reduces, so cold offset and hot offset are particularlyapt to occur. In view of the foregoing, the toner of the presentinvention, which is excellent in low-temperature fixability to someextent, preferably retains an appropriate viscosity even at hightemperatures.

It is preferable that: the step of forming the toner images include astep of transporting the toners to a developing portion with a tonercarrying member and a step of developing the electrostatic images withthe toners in the developing portion; and a ratio (Q_(K)/A_(K600)) ofthe absolute value for the charge quantity (Q_(K)) (mC/kg) of the toneron the toner carrying member in the transporting step to A_(K600) is22.0 to 50.0. In the present invention, a black toner having specificreflection spectral characteristics and more excellent in colordevelopment property than a conventional toner is used, but a toneramount with which an electrostatic latent image is developed ispreferably controlled in consideration of a relationship between thecolor development property and the charge quantity possessed by thetoner. That is, the following procedure is preferably adopted: as longas Q_(K)/A_(K600) falls within the above range, as A_(K600) of the tonerto be used increases, the value for Q_(K) is increased so that a toneramount used in the development of image data is reduced. With suchprocedure, the color development efficiency of the toner can beadditionally improved, and the resolution of an image is improved. Inaddition, a toner excellent in color development property is apt to showa remarkable image failure even when the toner scatters to a slightextent, so the following procedure is preferably adopted: as the colordevelopment property of the toner becomes more excellent, the chargequantity of the toner is increased so that an image failure such astoner scattering owing to charge defect is suppressed. Further, as thecolor development property of the toner becomes more excellent, thedisturbance of an edge portion of, for example, a dot image or lineimage is more liable to be remarkable. However, when the charge quantityof the toner is retained in a certain range in association with thecolor development property of the toner, the disturbance of the edgeportion is suppressed, and a reduction in resolution of the image iseasily suppressed. When Q_(K)/A_(K600) described above is less than22.0, the charge quantity of the toner is so small as compared to thecolor development property of the toner that a toner amount to be usedin the development of an image increases, and, even when the imagedensity of the image is sufficient, the resolution of the image mayreduce. Alternatively, the color development property of the toner is solarge as compared to the charge quantity of the toner that, even whenthe image resolution is sufficient, the color development efficiency ofthe colorant of the toner reduces, and a representable color spacenarrows in some cases. When Q_(K)/A_(K600) described above exceeds 50.0,the charge quantity of the toner is so large as compared to the colordevelopment property of the toner that a toner amount to be used in thedevelopment of an image is excessively small, and, even when the imagedensity of the image is sufficient, the coarseness of a highlightportion, the disturbance of an edge portion of a line image, or the likeis apt to be remarkable. Alternatively, the color development propertyof the toner is so small as compared to the charge quantity of the tonerthat, even when the image resolution is sufficient, the image density orimage color gamut of the image may be insufficient. Accordingly,Q_(K)/A_(K600) described above is more preferably 23.0 to 50.0, stillmore preferably 30.0 to 50.0, or still more preferably 36.0 to 50.0.

In the image-forming method of the present invention, M1_(x) (mg/cm²)described above is preferably (0.10×ρ_(TK)) to (0.40×ρ_(TK)) mg/cm²because a toner consumption is reduced, and the effects of the presentinvention is favorably exerted. When M1_(K) is less than (0.10×ρ_(TC))mg/cm², the toner penetrates into paper, and the representable colorspace of an image narrows in some cases. Alternatively, the number oftoner particles of which the image is formed reduces, and the uniformityof the image reduces in some cases. When M1_(K) exceeds (0.40×ρ_(TK))mg/cm², the resolution of the image is apt to reduce. In addition, whena transfer material having a small elastic modulus is used, the windingof paper as the transfer material in the fixing step is apt to occur.Accordingly, the above range of M1_(K) is more preferably (0.12×ρ_(TK))to (0.35×ρ_(TK)) mg/cm², or particularly preferably (0.15×ρ_(TK)) to(0.30×ρ_(TK)) mg/cm².

In the step of forming the toner images, a ratio (H_(K80)/H_(K20)) ofthe average height (H_(K80)) of the toner layer of a toner image formedon the electrostatic image bearing member for image data having a blackmonochromatic density of 80% to the average height (H_(K20)) of thetoner layer of a toner image formed on the electrostatic image bearingmember for image data having a black monochromatic density of 20% ispreferably 0.90 to 1.30. According to the present invention, anadditional improving effect on an image resolution is obtained, glossnon-uniformity is suppressed, an image with suppressed surfaceunevenness is obtained irrespective of the thickness of the transfermaterial, and a toner consumption can be reduced. When a toner excellentin color development property is used like the present invention, thetinge of an image at a certain point of the image is largely changed bythe number of toner particles present in the direction perpendicular toan image surface at the point. Accordingly, in the present invention,such image-forming method as described below is preferably employed: thenumbers of toner particles present in the directions perpendicular tothe surfaces of the respective gradation images are uniformized to theextent possible irrespective of the image densities of the images. WhenH_(K80)/H_(K20) described above is less than 0.90 or exceeds 1.30, arange from the highlight portion to halftone portion of an image becomessusceptible to image non-uniformity caused by changing in tinges owingto the non-uniformity of the number of toner particles present in thedirection perpendicular to the surface of the image. In particular, whenH_(K80)/H_(K20) exceeds 1.30, the resolution of a high-density gradationportion is apt to reduce, and the reproducibility of an image for imagedata is apt to reduce. Accordingly, H_(K80)/H_(K20) described above ispreferably 0.95 to 1.20, or particularly preferably 1.00 to 1.15. Suchimage formation is effective in an image-forming method in which imageformation based on an area coverage modulation method where gradation isrepresented on the basis of the area of an image region is adopted overa range from a low-density region to a high-density solid image region.

Next, an image-forming apparatus preferable for the present inventionwill be shown.

(1) Example of Image-Forming Apparatus

FIG. 3 is an outline constitution view showing an example of animage-forming apparatus for forming a full-color image by anelectrophotographic method. The image-forming apparatus of FIG. 3 isused as a full-color copying machine or full-color printer. In the caseof a full-color copying machine, as shown in FIG. 3, the apparatus has adigital color image reader portion at its upper portion and a digitalcolor image printer portion at its lower portion.

In the image reader portion, a manuscript 101 is mounted on a manuscriptboard glass 102, and is exposed to and scanned with an exposure lamp103, whereby a reflected light image from the manuscript 101 isconverged on a full-color sensor 105 by a lens 104, and a colorseparation image signal is obtained. The color separation image signalpasses through an amplifier circuit (not shown), is processed in a videoprocessing unit (not shown), and is sent to the digital image printerportion.

In the image printer portion, a photosensitive drum 106 as an imagebearing member has, for example, a photosensitive layer having anorganic photoconductor, and is rotatably supported in the directionindicated by an arrow. Arranged around the photosensitive drum 106 are apre-exposure lamp 107, a corona charging device 108, a laser exposureoptical system 109, a potential sensor 110, four developing devices111Y, 111C, 111M, and 111K containing toners different from one anotherin color, means 112 for detecting a light quantity on the drum, atransferring device 113, and a cleaning device 114.

In the laser exposure optical system, an image signal from the readerportion is converted into an optical signal for image scan exposure in alaser output portion (not shown), and the converted laser light isreflected on a polygon mirror 109 a, and is projected onto the surfaceof the photosensitive drum 106 through a lens 109 b and a mirror 109 c.

The printer portion rotates the photosensitive drum 106 in the directionindicated by the arrow at the time of image formation, negativelycharges the photosensitive drum 106 in a uniform manner with thecharging device 108 after the antistatic treatment of the drum with thepre-exposure lamp 107, and irradiates each separated color with anoptical image E to form an electrostatic image on the photosensitivedrum 106.

Next, a predetermined developing device is actuated to develop theelectrostatic image on the photosensitive drum 106, whereby a tonerimage is formed with a toner on the photosensitive drum 106. Thedeveloping devices 111Y, 111C, 111M, and 111K alternatively approach thephotosensitive drum 106 in accordance with the respective separatedcolors by virtue of the operations of their eccentric cams 115Y, 115C,115M, and 115K so as to perform development.

The transferring device has a transferring drum 113 a, a transfercharging device 113 b, an adsorption charging device 113 c forelectrostatically adsorbing a recording material and an adsorbing roller113 g opposed to the device 113 c, an inner charging device 113 d, anouter charging device 113 e, and a separation charging device 113 h. Thetransferring drum 113 a is rotatably pivoted, and a transfer sheet 113 fas a transfer material bearing member for bearing a transfer material istensioned at the opening portion of the peripheral surface of the drumso as to be integral with the upper portion of the cylinder of the drum.A resin film such as a polycarbonate film is used as the transfer sheet113 f.

The transfer material is transported from a cassette 116 a, 116 b, or116 c to the transferring drum 113 a through a transfer sheettransporting system, and is mounted on the transferring drum 113 a. Thetransfer material mounted on the transferring drum 113 a is repeatedlytransported to a transferring position opposed to the photosensitivedrum 106 in association with the rotation of the transferring drum 113a, and the toner image on the photosensitive drum 106 is transferredonto the transfer material by virtue of the action of the transfercharging device 113 b during the passage of the transfer materialthorough the transferring position.

The toner image may be directly transferred from the photosensitivemember onto the transfer material. Alternatively, the followingprocedure may be adopted: the toner image on the photosensitive memberis transferred onto an intermediate transfer body, and the toner imageis transferred from the intermediate transfer body onto the transfermaterial.

The above image-forming step is repeated for yellow (Y), magenta (M),cyan (C), and black (K) toners, and a color image obtained bysuperimposing four toner images on the transfer material on thetransferring drum 113 a is obtained.

The transfer material onto which the four toner images have beentransferred as described above is separated from the transferring drum113 a by virtue of the action of each of a separation claw 117 a, aseparation pushup roller 117 b, and the separation charging device 113 hso as to be sent to a heat pressure fixing unit 100 where the images arefixed under heat and pressure so that the color mixture, colordevelopment, and fixing to the transfer material of the toners areperformed, and a full-color fixed image is obtained. After that, thetransfer material is discharged to a tray 118, whereby the formation ofthe full-color image is completed.

A binarizing approach in the present invention will be described.

Various methods have been proposed as binarizing approaches forgradation reproduction. Methods to be most frequently employed inordinary cases are a dither method and a dot pattern method. The dithermethod involves causing one pixel of a read input signal to correspondto one pixel of binary recording as shown in FIG. 9(a).

The dot pattern method involves causing one pixel of a read input signalto correspond to multiple recorded pixels as shown in FIG. 9(c).

An approach intermediate between both the methods is a method involvingcausing one pixel of a read input signal to correspond to a partialmatrix (L×L) in an m×m matrix as shown in FIG. 9(b). In thecorrespondence to the partial pixel, L=1 corresponds to the dithermethod, L=m corresponds to the dot pattern method, and an output imagesize can be changed by taking an arbitrary value for L.

A dither pattern for each color is formed by employing such binarizingapproach. A halftone dot having a screen angle can be produced in adither pattern for each color by placing basic halftone dots (basiccells) each composed of a×a pixels while appropriately displacing thehalftone as shown in FIG. 10. When a displacement value (displacementvector) is represented by u=(a, b), a screen angle θ to be obtained canbe determined from the following expression.θ=tan^(−1(b/a))

A square threshold matrix size (N) corresponding to one cycle of thedots can be determined from the following expression using the values aand b for such displacement vector u.N=LCM(a,b)×(b/a+a/b)

It should be noted that LCM(a, b) represents the least common multipleof a and b. As small a matrix size as possible is preferably used inorder that a dither pattern having a desired angle may be realized, anda burden on hardware may be alleviated.

In the present invention, providing different screen angles for therespective colors has, for example, the following effects: theuniformity of the respective colors can be maintained even when thepositions of the colors are shifted, and the generation of moire fringescan be suppressed. In particular, the generation of moire fringes islargely affected by a combination of the screen angles of the respectivecolors. A preferable combination of screen angles in the presentinvention is as follows: when yellow is 0°, cyan (or magenta) is 14 to22°, black is 41 to 49°, and magenta (or cyan) is 68 to 76°. Thefollowing combination is particularly preferable: when yellow is 0°,cyan (or magenta) is 16 to 20°, black is 43 to 47°, and magenta (orcyan) is 69 to 73°.

FIG. 12 shows an example of the arrangement of dither pattern latticepoints which can be preferably used in the present invention. In thearrangement, the following setting is established: yellow (0°, 150lines), cyan (18.43°, 189 lines), black (45.00°, 122 lines), and magenta(71.57°, 189 lines).

In addition, a screen angle is preferably provided by providing a phasedifference for the above-mentioned pulse width modulation system (PWMsystem).

In addition, the dither pattern forming approach employed in the presentinvention allows multiple levels to be output. The following procedurehas only to be adopted: multiple dither matrix patterns are prepared, aninput pixel value and the threshold of each dither matrix pattern arecompared with each other, and the gradation of a matrix patternexceeding the threshold is output. The lighting width of a laser pulseat that time is controlled by gradation; the lighting position of thepulse at that time can be set in consideration of a “center, left, orright” in a pixel, and the position of a pixel in the matrix pattern andan influence of a peripheral pixel around the pattern.

The perimeter of a rasterized image in the present invention isdetermined on the assumption that the halftone pixel of a multi-levelimage is also one pixel. Although the position of a dot may shift to the“center, left, or right” in one pixel owing to the above change inlighting position, even a halftone image is converted into one pixelwith an output resolution (such as 600 dpi or 1,200 dpi) as a basicunit.

In the present invention, a halftone dot dither system in which the sizeof a halftone dot is changed, or a diffusion dither system in which thenumber of halftones dots is changed while the size of each halftone dotis not changed can be used.

In the present invention, the diffusion dither system is more preferablyused. An image density in a dot system is determined by the area ratioof dots. That is, as the area of the dots increases, the image densityincreases, but the use of the diffusion dither system enables arepresentable color space to be enlarged upon formation of a full-colorimage. In the present invention, a toner having high color developmentproperty is used. When the respective color toners are each a tonerhaving high color development property, the color development efficiencyof a toner present in a lower layer on a transfer material is apt toreduce owing to an influence of a toner present in an upper layer on thematerial. Accordingly, the use of the diffusion dither system allows aportion where the respective color toner layers are superimposed to beadditionally reduced, and enables the toners to exert their colordevelopment properties to the fullest extent possible. In addition, whena fine-line image is formed with a toner having high color developmentproperty, the nick or edge portion of each halftone dot of which a fineline is formed is apt to be remarkable, but the use of the diffusiondither system improves fine-line reproducibility, and can increase aresolution. In addition, the use can reduce a toner usage.

A film fixing system is preferably used as a heat fixing method in theimage-forming method of the present invention. Specific examples of thefilm fixing system include an SURF fixing system and an IHF fixingsystem. That is, the following fixing method is preferable: heatpressure means having at least a rotatable heating body surrounded by aheat-resistant film and a pressure roller as a pressure member is used,the pressure roller and the heat-resistant film are brought into contactwith each other to form a nip portion, and a recording material istransported while being sandwiched between the film and the pressureroller at the nip portion so that a fixed image is formed. When a tonerhaving high color development property is used while its usage isreduced like the present invention, the toner penetrates into a transfermaterial such as paper in the fixing step, and image appearance reducesin some cases. A film fixing system which: reduces the pressure to beapplied to the toner at the nip portion; and can enlarge a nip width ispreferable.

FIG. 4 shows an example of a fixing apparatus that realizes the SURFfixing system. The fixing apparatus has a heating device 4 and apressure roller 10 provided so as to be opposed to the device. Theheating device 4 has: a cylindrical heat-resistant film 5 made ofpolyimide coated with a fluorine resin or the like and having athickness around 50 μm; and a ceramic heater 7 as a heating body and atemperature detecting element 6 such as a thermistor placed in contactwith the heater to adjust the temperature at which toner is heated. Thepressure roller (pressure member) 10 has a mandrel 9 made of an aluminumalloy and a rubber roller 8 which: is placed on the outside of theperipheral surface of the mandrel; and is coated with a resincomposition excellent in releasing performance and heat resistance suchas a silicone resin or a fluorine resin.

The pressure roller 10 is provided while being biased by biasing means(not shown) such as a spring toward the heating surface of the ceramicheater (heating means) 7. The heat-resistant film 5 is provided so as tobe movable along an endless orbital (circular orbital in the shown form)passing through the upper portion of the heating surface of the ceramicheater. The heat-resistant film 5 is sandwiched between the ceramicheater 7 and the pressure roller 10 to form a nip portion between thefilm and the pressure roller 10. A recording material having an unfixedtoner image is introduced into the nip portion, whereby toner on therecording material melts, and a fixed toner image is formed on therecording material.

FIG. 5 shows an example of a fixing apparatus that realizes the IHFfixing system. The fixing apparatus has a fixing belt 11 and a pressureroller (pressure member) 12 provided so as to be opposed to the belt.The fixing belt 11 has a metal conductor 20 and an elastic layer 19 madeof a fluorine resin or the like with which the surface of the conductoris coated. An excitation coil 13 is placed in the fixing belt 11 so asto be concentric with the belt. In addition, a core 14 formed of amagnetic substance and serving as a magnetic field-shielding member forshielding a magnetic field is placed in the fixing belt 11. The pressureroller 12 has a hollow mandrel 21 made of an aluminum alloy and asurface releasable heat-resistant elastic layer 22 with which theoutside of the peripheral surface of the mandrel is coated.

The core 14 is supported by a pair of holders 15 each having a fansectional shape. The holders 15 are each formed of a heat-resistantresin such as polyphenylene sulfide (PPS), polyether ether ketone(PEEK), or a phenol resin. The excitation coil 13 is formed by winding awire along the surface of each of the holders 15 so that the coil is ofsuch a structure that the wire travels along the inner peripheralsurface of the fixing roller from the central protruded portion of thecore 14 having a “T”-shaped section.

A temperature sensor 16 is placed in contact with the surface of thefixing belt 11. In addition, a transport guide 17 is placed at aposition for guiding a recording material having an unfixed toner imageto a pressure contact portion (nip portion) between the fixing belt 11and the pressure roller 12. In addition, a separation claw 18 isprovided in the rear of the fixing apparatus. The separation claw 18 isplaced in contact with, or close to, the surface of the fixing belt 11to prevent the recording material such as paper from winding around thefixing belt 11.

The pressure roller 12 is provided while being biased by biasing means(not shown) such as a spring toward the fixing belt 11 (core 14). Thefixing belt 11 is provided so as to be movable along an endless orbital(circular orbital in the shown form) passing while facing the excitationcoil 13. The fixing belt 11 is sandwiched between the core 14 and thepressure roller 12 at its portion opposed to the pressure roller 12 toform a nip portion between the belt and the pressure roller 12. Arecording material having an unfixed toner image is introduced into thenip portion, whereby toner on the recording material melts, and a fixedtoner image is formed on the recording material.

The excitation coil 13 generates a high-frequency magnetic field byflowing a high-frequency current in the coil. The magnetic fieldgenerates an induced eddy current in the fixing belt 11 to cause thefixing belt 11 to undergo Joule heating by virtue of the skin resistanceof the fixing belt itself. In the apparatus, the excitation coil and aseries of devices that flows a high-frequency current in the excitationcoil are said to be heating means. The temperature of the fixing belt 11is automatically controlled to a constant temperature by increasing ordecreasing power supply to the excitation coil 13 on the basis of asignal detected by the temperature sensor 16.

In addition, the high-frequency magnetic field can be efficientlygenerated by combining the excitation coil 13 with the core 14 composedof a magnetic substance. In particular, when a core having a “T”-shapedsection is used like the form shown in FIG. 5, a heat quantity neededfor the fixing apparatus can be generated with low power by virtue ofthe effective concentration of the high-frequency magnetic field or ashielding effect on a magnetic field to a portion except aheat-generating portion.

A material for the elastic layer 19 is, for example, a fluorine resin ora silicone resin. Specific examples of the material include atetrafluoroethylene/perfluoroalkylvinylether copolymer (PFA),polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), a vinylidenefluoride fluorocarbon rubber, a propylene/tetrafluoroethylenefluorocarbon rubber, a fluorosilicone rubber, and a silicone rubber.

The thickness of the elastic layer 19 is preferably 10 to 500 μm inorder that gloss non-uniformity due to the fact that the heating surfaceof heating means cannot follow the unevenness of the recording materialor the unevenness of a toner layer upon printing of an image may beprevented.

When the thickness of the elastic layer 19 is less than 10 μm, the layercannot exert its function as an elastic member, and a pressuredistribution at the time of fixation becomes non-uniform, so an unfixedtoner having a secondary color cannot be sufficiently fixed under heatparticularly at the time of the fixation of a full-color image, and thegloss non-uniformity of a fixed image arises. Moreover, the color mixingproperty of toners deteriorates owing to the insufficient melting of thetoners, with the result that a high-definition full-color image cannotbe obtained. Accordingly, a thickness of less than 10 μm is notpreferable. In addition, when the thickness of the elastic layer 19exceeds 500 μm, thermal conductivity at the time of fixation isinhibited, and heat followability at a fixing surface reduces, with theresult that quick start property reduces, and fixation non-uniformity isapt to arise. Accordingly, a thickness in excess of 500 μm is notpreferable either.

Next, methods of measuring the respective physical properties concerningthe toner of the present invention will be described below.

(Measurement of True Density of Toner)

The true density of the toner can be measured by a method involving theuse of a gasreplacement type pycnometer. The measurement principle is asdescribed below. A shut-off valve is provided between a sample chamber(having a volume V₁) and a comparison chamber (having a volume V₂) eachhaving a constant volume, and the mass (M₀ (g)) of a sample is measuredin advance before the sample is loaded into the sample chamber. Theinside of each of the sample chamber and the comparison chamber isfilled with an inert gas such as helium, and a pressure at that time isrepresented by P₁. The shut-off valve is closed, an inert gas is addedonly to the sample chamber, and a pressure at that time is representedby P₂. A pressure in a system when the shut-off valve is opened so thatthe sample chamber and the comparison chamber are connected to eachother is represented by P₃. The volume (V₀ (cm³) of the sample can bedetermined from the following expression A. The true density ρ_(T)(g/cm³) of the toner can be determined from the following expression B.V ₀ =V ₁ −[V ₂/{(P ₂ −P ₁)/(P ₃ −P ₁)−1}]  (Ex. A)ρ_(T) =M ₀ /V ₀  (Ex. B)

The true density can be measured with, for example, a dry automaticdensimeter Accupyc 1330 (manufactured by Shimadzu Corporation). At thattime, a 10-cm³ sample container is used, a helium gas purge as a samplepretreatment is performed at a maximum pressure of 19.5 psig (134.4 kPa)ten times. After that, a fluctuation in pressure in the sample chamberof 0.0050 psig/min is used as an index for judging whether the pressurein the container reaches equilibrium. If the fluctuation is equal to orlower than the value, the pressure is regarded as being in anequilibrium state, so measurement is initiated, and the true density isautomatically measured. The measurement is performed five times, and theaverage of the five measured values is determined and defined as thetrue density (g/cm³).

(Measurement of Viscosity (η₁₀₅) of Toner at 105° C. and Viscosity (η₁₂₀of Toner at 120° C.)

The viscosities of the toner at 105° C. and 120° C. can be measured witha constant-load capillary extrusion rheometer. The method involvesmeasuring an extrusion resistance when a molten substance passes througha capillary to measure the viscosity of the molten substance.

The measurement principle is as described below. A sample loaded into acylinder is heated, and a constant pressure P is applied from above thesample by a piston. When the sample is heated to a certain temperatureor higher, the sample is extruded through a capillary provided for thebottom portion of the cylinder. The viscosity η (Pa·s) of the toner ateach temperature can be determined from the following expression byusing an outflow Q (cm³/s) and a pressure at that time:Outflow Q=A×(S ₂ −S ₁)/((t ₂ −t ₁)×10)where S₁ represents the position (mm) of the piston at a time t₁ (s), S₂represents the position (mm) of the piston at a time t₂ (s), and Arepresents the sectional area (cm²) of the piston;Viscosity η=π×D ⁴ ×P/(128,000×L×Q)where P represents a pressure (Pa), D represents the diameter (mm) ofthe capillary, and L represents the length (mm) of the capillary.

To be specific, the measurement is performed with, for example, a FlowTester CFT-500D (manufactured by Shimadzu Corporation) under thefollowing conditions.

Sample: When the true density of the toner is represented by ρ, (1.5×ρ)g of the toner are weighed, and the toner is subjected to pressuremolding with a pressure molder under a normal-temperature,normal-pressure environment at a load of 200 kgf (1,960N) for 2 minutesinto a cylinder having a diameter of about 10 mm and a height of about15 mm to be used as a sample.Cylinder pressure: 4.90×10⁵ (Pa)Measurement mode: temperature increase methodRate of temperature increase: 4.0° C./min

The viscosity can be measured with a mirror-abraded die having a lengthof 1.0 mm and a diameter of 0.3 mm, 0.5 mm, 1.0 mm, or 1.5 mm. When eachdie is used, the viscosities of the toner at 40° C. to 200° C. aremeasured, and a value determined by one measurement is used for each ofthe viscosity at 105° C. and the viscosity at 120° C.

(Measurement of Molecular Weight in Toner, Binder Resin, Wax, and theLike by Gel Permeation Chromatography (GPC))

As described below, a molecular weight distribution of binder resin inthe toner, and resin part of wax dispersion medium by GPC can bedetermined through measurement by GPC using THF soluble matter obtainedby dissolving a sample as a measuring object in a tetrahydrofuran (THF)solvent.

When a true density of a sample to be measured is defined as ρ, (25×ρ)mgof the sample is put in 5 ml of THF, and the sample is left for 24hours. Then, the mixture is passed through a sample treatment filter(having a pore size of 0.45 to 0.5 μm, for example, Mishoridisk H-25-5manufactured by Tosoh Corporation or Ekicrodisk 25 CR manufactured byGelman Science Japan) to prepare a sample for GPC measurement. GPCmeasurement of the sample prepared by the above method is as follows. Acolumn is stabilized in a heat chamber at 40° C., and THF to serve as asolvent is flown to the column stabilized at the temperature at a flowvelocity of 1 ml/min. Then, about 100 μl of the sample solution isinjected for measurement.

A combination of multiple commercially available polystyrene gel columnsis preferably used as a column for accurately measuring a molecularweight region of 10³ to 2×10⁶. Preferable examples of the combination ofcommercially available polystyrene gel columns include: a combination ofshodex GPS KF-801, 802, 803, 804, 805, 806, and 807 manufactured byShowa Denko K.K.; and a combination of μ-styragel 500, 10³, 10⁴, and 10⁵manufactured by Waters Corporation. RI (A refractive index) detector isused as a detector.

In measuring the molecular weight of the sample, the molecular weightdistribution possessed by the sample is calculated from a relationshipbetween a logarithmic value for a calibration curve prepared by severalkinds of monodisperse polystyrene standard samples and the number ofcounts (Retention time). Examples of the standard polystyrene samplesfor preparing a calibration curve to be used include samplesmanufactured by TOSOH CORPORATION or by Pressure Chemical Co. eachhaving a molecular weight of 6×10², 2.1×10³, 4×10³, 1.75×10⁴, 5.1×10⁴,1.1×10⁵, 3.9×10⁵, 8.6×10⁵, 2×10⁶, or 4.48×10⁶. At least about tenstandard polystyrene samples are suitably used.

(Measurement of Molecular Weight of Wax by GPC)

Device: GPC-150C (manufactured by Waters Corporation)

Column: GMH-MT 30 cm×2 (manufactured by Tosoh Corporation)

Temperature: 135° C.

Solvent: o-dichlorobenzene (added with 0.1% of IONOL)

Flow rate: 1.0 ml/min

Sample: 0.4 ml of a 0.15 wt % wax is injected.

The measurement is performed under the above-described conditions. Uponcalculation of the molecular weight of the wax, a molecular weightcalibration curve created from a monodisperse polystyrene standardsample is used. Furthermore, the molecular weight of the wax iscalculated through polyethylene conversion by using a conversionequation deduced from a Mark-Houwink viscosity equation.

(Measurement of Glass Transition Point (Tg), and Temperature, Endotherm,and Half Width of Highest Endothermic Peak)

In the present invention, a glass transition point (Tg), and thetemperature, endotherm, and half width of the highest endothermic peakare measured with a differential scanning calorimeter (DSC). To bespecific, for example, a Q1000 (manufactured by TA Instruments) can beutilized as a DSC. A measurement method is as described below. 4 mg of asample are precisely weighed in an aluminum pan, and measurement isperformed by using an empty aluminum pan as a reference pan under anitrogen atmosphere at a modulation amplitude of 1.0° C. and a frequencyof 1/min. A reversing heat flow curve obtained by scanning at ameasurement temperature retained at 10° C. for 10 minutes and thenincreased at a rate of temperature increase of 1° C./min from 10° C. to180° C. is defined as a DSC curve, and Tg is determined from the curveby a middle point method. It should be noted that a glass transitiontemperature determined by the middle point method is defined as a pointof intersection of a middle line, which is placed between a base linebefore an endothermic peak and a base line after the endothermic peak,and a rise-up curve in a DSC curve at the time of temperature increase(see FIG. 6).

The temperature, endotherm, and half width of the highest endothermicpeak of the toner are measured as described below. In a reversing heatflow curve obtained as a result of the same measurement as describedabove, a straight line is drawn to connect the point at which anendothermic peak leaves the extrapolated line of a base line before theendothermic peak and the point at which the extrapolated line of thebase line after the completion of the endothermic peak and theendothermic peak contact with each other. The temperature at which theendothermic peak shows a local maximum value in the region surrounded bythe straight line and the endothermic peak is defined as the temperatureof the highest endothermic peak. When the peak shows two or more localmaximum values, the temperature at the local maximum value that is mostdistant from the connecting straight line in the surrounded region isdefined as the temperature of the highest endothermic peak. When two ormore independent surrounded regions are present, the temperature at thelocal maximum value that is most distant from a straight line connectingpoints in the same manner as that described above is similarly definedas the temperature of the highest endothermic peak. In addition, thehalf width of the highest endothermic peak is defined as the temperaturewidth of a line connecting a point, which corresponds to one half of thelength between a straight line connecting points in the same manner asthat described above and a local maximum value in the highestendothermic peak specified by the above method, and a DSC curve at alower temperature than that of the local maximum value.

The endotherm is determined as described below. In the reversing heatflow curve obtained by the above measurement, a straight line is drawnto connect the point at which an endothermic peak leaves theextrapolated line of a base line before the endothermic peak and thepoint at which the extrapolated line of the base line after thecompletion of the endothermic peak and the endothermic peak contact witheach other. The area of the region surrounded by the straight line andthe endothermic peak (integration value of a melt peak) is determined tobe the endotherm (J/g). When two or more independent surrounded regionsare present, the sum of the areas of the regions is defined as theendotherm.

<Measurement of Average Circularity of Toner>

The average circularity of toner is measured with a flow-type particleimage analyzer “FPIA-2100 type” (manufactured by SYSMEX CORPORATION) andis calculated from the following equation.Circle-equivalent diameter=(particle projected area/π)^(1/2)×2Circularity=(perimeter of circle having same area as particle projectedarea)/(circumferential length of the projected image of aparticle)  [Formula 3]

where the “particle projected area” is defined as an area of a binarizedtoner particle image, and the “circumferential length of the projectedimage of a particle” is defined as a borderline drawn by connecting edgepoints of the toner particle image. When image processing, the peripherylength of the particle image in 512×512 image processing resolution(having pixels of 0.3 μm×0.3 μm) is used.

The roundness in the present invention is an indication for the degreeof irregularities of a toner particle. If the toner particle is of acomplete spherical shape, the roundness is equal to 1.000. The morecomplicated the surface shape, the lower the value for the roundness.

In addition, an average circularity C which means an average value of acircularity frequency distribution is calculated from the followingequation where ci denotes a circularity (center value) at a divisionpoint i in the particle size distribution and m denotes a number ofmeasured particles.

$\begin{matrix}{{{average}\mspace{14mu}{circularity}\mspace{14mu} C} = {\sum\limits_{i = 1}^{m}\;{{ci}/m}}} & \left\lbrack {{Formula}\mspace{14mu} 4} \right\rbrack\end{matrix}$

It should be noted that the “FPIA-2100” as a measuring apparatus used inthe present invention calculates the circularities of the respectiveparticles, classifies the particles into classes obtained by equallydividing a circularity range of 0.4 to 1.0 in an increment of 0.01depending on the resultant circularities upon calculation of an averagecircularity and a circularity standard deviation, and calculates theaverage circularity and the circularity standard deviation by using thecentral value of each division and the number of measured particles.

A specific measurement method is as follows. 10 ml of ion-exchangedwater from which an impurity solid or the like has been removed inadvance is charged in a vessel, and a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to the water. After that,0.02 g of a measurement sample is added to the mixture, and is uniformlydispersed. An ultrasonic dispersing unit “Tetoral 150” (manufactured byNIKKAKI BIOSCO., LTD.) is used as dispersing means, and the dispersiontreatment is performed for 2 minutes to prepare a dispersion formeasurement. At that time, the dispersion is appropriately cooled so asnot to have a temperature of 40° C. or higher. In addition, in orderthat a fluctuation in circularity may be suppressed, the temperature ofthe environment where the flow-type particle image analyzer FPIA-2100 isplaced is controlled to 23° C.±0.5° C. so that the temperature in theapparatus becomes 26 to 27° C., and automatic focusing is performed byusing 2-μm latex particles at a certain time interval, or preferablyevery 2 hours.

The flow type particle image measuring device is used for circularitymeasurement of the toner particles. The concentration of the dispersionis readjusted in such a manner that a concentration of color tonerparticles upon the measurement may be in the range of 3,000 to 10,000particles/μl. Then, 1,000 or more toner particles are measured. Afterthe measurement, an average circularity of the toner particles isdetermined by using the obtained data while cutting off data forparticles each having a circle-equivalent diameter of less than 2 μm.

(Weight-Average Particle Diameter (D4) of Toner, Particle DiameterDistribution (D4/D1), Content of Toner Particles Each Having ParticleDiameter More than Twice as Large as D4, and Content of Toner ParticlesEach Having Particle Diameter Less than One Half of D1)

A Coulter Multisizer IIE (manufactured by Beckman Coulter, Inc) is usedas a measuring apparatus. Measurement is performed by using an ISOTON(R)-II (1% aqueous solution of sodium chloride, manufactured by CoulterScientific Japan, Co.) as an electrolyte solution. A measurement methodis as described below. 0.1 to 5 ml of a surfactant (preferably analkylbenzene sulfonate) as a dispersant are added to 100 to 150 ml ofthe aqueous electrolyte solution. Further, 2 to 20 mg of a measurementsample are added to the mixture. The electrolyte solution in which thesample has been suspended is subjected to a dispersion treatment with anultrasonic dispersing unit for about 1 to 3 minutes, and the volumes andnumber of the particles of the toner are measured with the measuringapparatus so that the weight-average particle diameter of the toner iscalculated.

When the weight-average particle diameter is larger than 6.0 μm, thevolumes and number of particles each having a particle diameter of 2 to60 μm are measured with a 100-μm aperture. When the weight-averageparticle diameter is 3.0 to 6.0 μm, the volumes and number of particleseach having a particle diameter of 1 to 30 μm are measured with a 50-μmaperture. When the weight-average particle diameter is smaller than 3.0μm, the volumes and number of particles each having a particle diameterof 0.6 to 18 μm are measured with a 30-μm aperture.

(Method of Collecting Tetrahydrofuran (THF)-Soluble Component and Methodof Measuring Content of the Component)

The THF-soluble component of the toner means the mass ratio of anultrahigh molecular weight polymer component (substantially acrosslinked polymer) which has become insoluble in a THF solvent. Avalue measured as described below is defined as the content of theTHF-soluble component of the toner.

About 1 g of the toner is weighed (W₁ g). The weighed toner is placed inextraction thimble (such as No. 86R manufactured by Toyo Roshi), and isset in a Soxhlet extractor. The toner is extracted by using 200 ml ofTHF as a solvent in an oil bath at 80° C. for 12 hours, whereby anextracted solution is obtained. After THF in the extracted solution hasbeen removed by distillation, the remainder is dried in a vacuum at 40°C. for 3 days, and the THF-soluble component is weighed (W₂ g). Thecontent of the THF-soluble component of the toner is calculated from thefollowing expression.Content of THF-soluble component of toner(mass %)=W ₂×100/W ₁  [Formula5]

In addition, the THF-soluble component obtained by the above method isused in the measurement of the molecular weight of the toner and in themeasurement of a sulfur element derived from a sulfonic group.

(Method of Collecting Isopropanol-Soluble Component)

About 2 g of the toner are weighed (W₁ g). The weighed toner is placedin extraction thimble (such as No. 86R manufactured by Toyo Roshi), andis subjected to a Soxhlet extractor. The toner is extracted by using 200ml of isopropanol as a solvent for 12 hours. After isopropanol in asoluble component has been removed by distillation, the remainder isdried, whereby a sample is collected. The sample is defined as 100 mass% of a solvent-soluble component extracted with isopropanol. The timeperiod for extraction is changed, and a calibration curve showing arelationship between the time period for extraction and an extractedamount is created. Heating is stopped at a time corresponding to anextracted amount of 20 mass % on the basis of the calibration curve, anda flask containing the extract (Extract 1) is shifted to a flaskcontaining 200 ml of new isopropanol, and extraction is restarted.Heating is stopped when the total time period for extraction reaches 12hours, and an extract (Extract 2) is collected. The solvent in each ofExtract and Extract 2 is removed by distillation, and a firstsolvent-soluble component and a second-solvent soluble component arecollected from Extract 1 and Extract 2, respectively.

(Measurement of Sulfur Element Derived from Sulfonic Group)

The content of a sulfur element is measured with a wavelength dispersivefluorescent X-ray “Axios advanced” (manufactured by PANalytical). About3 g of the toner are loaded into a ring made of vinyl chloride for 27-mmmeasurement, and is pressed at 200 kN so as to be molded into a sample.The toner usage and the thickness of the sample after the molding aremeasured, and the content of a sulfur element derived from a sulfonicgroup in the toner is determined as an input value for contentcalculation. Analysis conditions and analysis are shown below.

Analysis Conditions

Determination method:fundamental-parameters method Elements to beanalyzed: Each of the elements ranging from boron to uranium in theperiodic table is subjected to measurement.

Measurement atmosphere: vacuum

Measurement sample: solid

Collimator mask diameter: 27 mm

Measurement condition: An automatic program set in advance to anexcitation condition optimal for each element was used.

Measuring time: about 20 minutes

General values recommended by the apparatus were used for the otherconditions.

Analysis

Analysis program: UniQuant5

Analysis condition: oxide form

Balance component: CH₂

General values recommended by the apparatus were used for the otherconditions.

(Method of Measuring Acid Value)

An acid value is determined as described below. A basic operation is inconformance with JIS-K0070. To be specific, a test is performed by thefollowing method.

(1) Reagent

(a) Solvent

A mixed liquid of ethyl ether and ethyl alcohol (1+1 or 2+1) or a mixedliquid of benzene and ethyl alcohol (1+1 or 2+1) is used as a solvent,and any such solution is neutralized with a 0.1-mol/L solution ofpotassium hydroxide in ethyl alcohol immediately before the use of thesolution by using phenolphthalein as an indicator.

(b) Phenolphthalein Solution

1 g of phenolphthalein is dissolved in 100 ml of ethyl alcohol (95 v/v%).

(c) 0.1-mol/L Solution of Potassium Hydroxide in Ethyl Alcohol

7.0 g of potassium hydroxide are dissolved in as small an amount aspossible of water. Ethyl alcohol (95 v/v %) is added to the solution sothat the mixture has a volume of 1 l. The mixture is left to stand for 2to 3 days, and is then filtrated. Standardization is performed inconformance with JIS K 8006 (basic item concerning titration duringcontent test for reagent).

(2) Operation

1 to 2 g of a sample are precisely weighed, and 100 ml of the solventand several drops of a phenolphthalein solution as an indicator areadded to the sample. The mixture is sufficiently shaken until the samplecompletely dissolves. In the case of a solid sample, the sample isdissolved by heating the mixture on a water bath. After having beencooled, the resultant is titrated with a 0.1-mol/L solution of potassiumhydroxide in ethyl alcohol, and the amount of the solution in which thefaint red color of the indicator continues for 30 seconds is defined asthe end point of the titration.

(3) Calculation Expression

The acid value of the sample is calculated from the followingexpression.A=(B×f×5.611)/S  [Formula 6]

In the expression, A represents the acid value, B represents the usage(ml) of the 0.1-mol/L solution of potassium hydroxide in ethyl alcohol,f represents the factor of the 0.1-mol/L solution of potassium hydroxidein ethyl alcohol, and S represents the sample (g).

(Charge Quantity of Toner)

A method of measuring the charge quantity of the toner is as describedbelow. In the case of development with a two-component developer havingthe toner and a carrier, the developer recovered from a toner carryingmember such as a developing sleeve is subjected to a blow-offmeasurement method for the determination of the charge quantity of thetoner. In the case of a one-component developer, the developer isdirectly subjected from a toner carrying member such as a developingsleeve to the blow-off measurement method for the determination of thecharge quantity of the toner. The blow-off measurement method can beperformed by a known method.

In the case of a two-component developer, in the present invention, thecharge quantity is preferably measured with a charge quantity measuringapparatus shown in FIG. 11.

FIG. 11 is an explanatory view of an apparatus for measuring thetriboelectric charge quantity of a two-component developer. First, ametallic measurement container 202 having, at its bottom, a screen 201having an aperture of 30 μm is filled with 0.5 to 1.5 g of atwo-component developer recovered from the upper portion of a sleeve,and is covered with a metallic lid 203. The mass of the entirety of themeasurement container 202 at that time is measured and represented by W1(g). Next, by using a sucking machine 204 (at least part of which incontact with the measurement container 202 is an insulator) suction isperformed from a suction port 205, and the pressure indicated by avacuum gauge 207 is set to 4 kPa by adjusting an air flow control valve206. Suction is performed in the state sufficiently, or preferably forabout 2 minutes so that the toner is sucked and removed. The potentialindicated by a potentiometer 208 at that time is represented by V(volt). Here, reference numeral 209 represents a capacitor which has acapacity of C (μF). In addition, the mass of the entirety of themeasurement container after the suction is measured and represented byW2 (g). The triboelectric charge quantity (mC/kg) of the toner iscalculated from the following expression.Triboelectric charge quantity (mC/kg) of two-componentdeveloper=C×V/(W1−W2).

In the case of a one-component developer, toner on a toner carryingmember such as a developing sleeve is directly sucked and subjected tomeasurement with a suction type charge quantity measuring apparatus(210HS-2A manufactured by TREK JAPAN). The mass W3 (kg) of a Faradaycage mounted with a filter is measured, the entire toner present in anarea of about 5 cm² on the toner carrying member is sucked, and the massW4 (kg) of the Faraday cage after the suction is measured. The chargequantity (mC/kg) of the toner is calculated from the followingexpression on the basis of a value q (mC) measured as a result of thesuction of the toner.Charge quantity (mC/kg) of toner=q/(W4−W3)

(Toner Amount on Electrostatic Image Bearing Member and Toner Amount onTransfer Material)

As in the above case of a one-component developer in the measurement ofthe charge quantity of toner, toner on an electrostatic image bearingmember and toner on a transfer material before fixation are eachdirectly sucked and subjected to measurement. After the entire tonerpresent in an area of about 5 cm² on a toner carrying member has beensucked, an area A (cm²) of the sucked portion is measured. A toneramount (mg/cm² i) is calculated from the following expression.Toner amount (mg/cm²)=(W4−W3)/A

(Measurement of Gloss of Image)

The gloss of an image can be measured with a commercially availabledevice. To be specific, the gloss can be measured with, for example, aPG-3D manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD. (incidentangle θ=75°). Black glass having a gloss value of 96.9 can be used incalibration with a standard sample.

(Measurement Chroma c* and Lightness L* of Image)

The chroma c* and lightness L* of an image can be measured with acommercially available device in accordance with the specifications ofthe CIELAB color coordinate system. To be specific, L*, a*, b*, c*, andh* can be determined as follows: a non-image portion is subjected tomeasurement with, for example, a SpectroScan Transmission (manufacturedby GretagMacbeth) as a reference, and then an image portion is subjectedto measurement. Specific measurement conditions are shown below.

Measurement Conditions

Observation light source: D50

Observation view angle: 2°

Density: DIN NB

White reference: Pap

Filter: No (absent)

It should be noted that, when the measuring apparatus does not displaythe chroma c*, the chroma can be calculated from the followingexpression.c*=√{square root over (a* ² +b* ²)}  [Formula 7]

(Measurement of Height of Toner Layer Developed on Electrostatic ImageBearing Member and Height of Toner Layer on Fixing Paper)

The height of a toner layer developed on an electrostatic image bearingmember and the height of a toner layer on fixing paper can each bedetermined by direct measurement with a commercially available opticalobserver. To be specific, each height can be measured with, for example,a color laser microscope (VK-9500, manufactured by KEYENCE CORPORATION).A distance between the point at which the height of a toner layer in thedirection perpendicular to a measuring surface (the electrostatic imagebearing member or the non-image portion of the fixing paper) shows alocal maximum value and the measuring surface is measured. The sameoperation is performed for 10 randomly sampled points, and the averageof the heights is defined as the height of the toner layer.

EXAMPLES

Hereinafter, the present invention will be described more specificallyby way of production examples and examples. However, the presentinvention is by no means limited to those examples.

(Sulfonic Acid Compound Production Example 1)

A mixture composed of the following materials was loaded into a reactionvessel equipped with a reflux pipe, a stirring machine, a temperaturegauge, a nitrogen introducing pipe, a dropping device, and adecompression device, and was polymerized at 70° C. for 10 hours whilebeing stirred. The solvent was removed by distillation, whereby a resinA was obtained.

Toluene: 200 parts by mass

Styrene: 90 parts by mass

Acrylic acid: 10 parts by mass

t-butylperoxy-2-ethylhexanoate: 3 parts by mass

The following materials were added to a reaction vessel equipped with areflux pipe, a stirring machine, a temperature gauge, a nitrogenintroducing pipe, a dropping device, and a decompression device, andwere heated at 120° C. for 6 hours while being stirred. After thecompletion of the reaction, the resultant was loaded into 600 parts bymass of ethanol, and the precipitate was collected. The resultantprecipitate was washed with hydrochloric acid and water, and was thendried, whereby a resin B was obtained.

Above resin A: 15 parts by mass

p-toluidine-2-sulfonic acid: 12 parts by mass

Pyridine: 320 parts by mass

Triphenyl phosphite: 36 parts by mass

The following materials were added to a reaction vessel equipped with areflux pipe, a stirring machine, a temperature gauge, a nitrogenintroducing pipe, a dropping device, and a decompression device, andwere cooled to 0° C. while being stirred. 44 parts by mass of a 2-mol/Lsolution of trimethylsilyl diazomethane in hexane (manufactured bySIGMA-ALDRICH) were added to the resultant, and the mixture was stirredfor 5 hours. After the solvent had been removed by distillation, theremainder was loaded into 3,000 parts by mass of methanol, and theprecipitate was collected and dried, whereby a sulfonic acid compound 1represented by the following chemical formula was obtained. Theresultant sulfonic acid compound 1 had a number average molecular weightof 11,200, a weight-average molecular weight of 13,700, a glasstransition temperature of 86.7° C., and an acid value of 6.8 mgKOH/g.

Above resin B: 100 parts by mass

Chloroform: 400 parts by mass

Methanol: 100 parts by mass

(Sulfonic Acid Compound Production Example 2)

The following materials were added to a reaction vessel equipped with areflux pipe, a stirring machine, a temperature gauge, a nitrogenintroducing pipe, a dropping device, and a decompression device, andwere heated to 80° C. while being stirred.

Methanol: 300 parts by mass

2-butanone: 150 parts by mass

2-propanol: 150 parts by mass

Styrene: 76 parts by mass

2-ethylhexyl acrylate: 12 parts by mass

2-acrylamide-2-methylpropanesulfonic acid: 12 parts by mass

A solution composed of the following materials was dropped to theresultant over 30 minutes, and the mixture was continuously stirred foran additional 10 hours. After that, 600 parts by mass of deionized waterwere added to the mixture while the temperature was maintained, and thewhole was stirred for 2 hours while attention was paid in order that aninterface between an organic layer and a water layer might not bedisturbed. After the water layer had been wasted, the solvent wasremoved by distillation under reduced pressure. The remainder was driedunder reduced pressure, whereby a sulfonic acid compound 2 was obtained.The resultant sulfonic acid compound 2 had a number average molecularweight of 15,300, a weight-average molecular weight of 24,300, a glasstransition temperature of 61.2° C., and an acid value of 18.4 mgKOH/g.t-butylperoxy-2-ethylhexanoate: 1 part by mass2-butanone: 20 parts by mass

(Cyan Toner Production Example 1)

Styrene 70 parts by mass n-butyl acrylate 30 parts by mass Pigment Blue15:3 12 parts by mass Aluminum salicylate compound 1 part by mass(BONTRON E-88: manufactured by Orient Chemical Industries, LTD.)Sulfonic acid compound 1 1.8 parts by mass Divinylbenzene 0.01 part bymass Resin 1 obtained in Resin Production Example 1 25 parts by mass tobe described later Wax 1 shown in Table 1 8 parts by mass Toluene 10parts by mass

A mixture composed of the above components was prepared. 100 parts bymass of glass beads each having a diameter of 1 mm were added to themixture, and the whole was dispersed with a paint shaker for 12 hourswhile the extent to which the whole was heated was suppressed with coldair. The glass beads were removed, whereby a monomer dispersion liquidwas obtained.

900 parts by mass of ion-exchanged water and 3.5 parts by mass oftricalcium phosphate were added to a container equipped with ahigh-speed stirring device TK-homomixer (manufactured by Tokushu KikaKogyo). The number of revolutions of the device was adjusted to 10,000revolutions/min, and the mixture was heated to 70° C., whereby adispersion medium system was obtained.

parts by mass of t-butylperoxy-2-ethylhexanoate (TBEH) as apolymerization initiator and 1 part by mass of disuccinic acid peroxide(DSAP) as a polymerization initiator and an acid value-imparting agentwere added to the above monomer dispersion liquid, and the mixture wasloaded into the above dispersion medium system. The resultant wassubjected to a granulating step with the high-speed stirring device for5 minutes while the number of revolutions was maintained at 15,000revolutions/min. After that, the resultant was polymerized for 12 hourswith a propeller stirring blade used as a stirring machine instead ofthe high-speed stirring device at 150 revolutions/min. The resultant washeated to 90° C., and was stirred for 2 hours while the pressure in thecontainer was reduced to 50 kPa. Then, toluene was removed bydistillation. After that, the remainder was cooled to 30° C. at acooling rate of 1.5° C./min. The resultant was filtrated, washed, dried,and classified, whereby toner particles were obtained.

Above toner particles 100 parts by mass Hydrophobic titanium oxidetreated with n-C₄H₉Si(OCH₃)₃ (BET specific surface area: 120 m²/g)

-   -   1 part by mass        Hydrophobic silica treated with hexamethyldisilazane and then        with silicone oil (BET specific surface area: 160 m²/g) 1 part        by mass

A mixture composed of the above components was mixed with a Henschelmixer, whereby Cyan Toner 1 was obtained. Tables 5, 6, and 7 show thephysical properties of the toner.

(Cyan Toner Production Examples 2 to 4)

Cyan Toners 2 to 4 were each obtained in the same manner as in CyanToner Production Example 1 except that conditions in Cyan TonerProduction Example 1 were changed as shown in Table 3. Tables 5, 6, and7 show the physical properties of the toners.

(Cyan Toner Production Example 5)

Styrene 70 parts by mass n-butyl acrylate 30 parts by mass Colorant usedin Cyan toner 1 12 parts by mass Aluminum salicylate compound 1 part bymass (BONTRON E-88: manufactured by Orient Chemical Industries, LTD.)Sulfonic acid compound 1.6 parts by mass Divinylbenzene 0.02 part bymass Resin 1 obtained in Resin Production Example 1 3 parts by mass tobe described later Wax 1 shown in Table 1 8 parts by mass

A mixture composed of the above components was prepared. The whole wasdispersed for 12 hours with a propeller stirring blade used as astirring machine at 150 revolutions/min while the extent to which thewhole was heated was suppressed with cold air, whereby a monomerdispersion liquid was obtained.

900 parts by mass of ion-exchanged water and 3.5 parts by mass oftricalcium phosphate were added to a container equipped with ahigh-speed stirring device TK-homomixer (manufactured by Tokushu KikaKogyo). The number of revolutions of the device was adjusted to 10,000revolutions/min, and the mixture was heated to 80° C., whereby adispersion medium system was obtained.

4 parts by mass of t-butylperoxy-2-ethylhexanoate (TBEH) as apolymerization initiator and 1 part by mass of disuccinic acid peroxide(DSAP) as a polymerization initiator and an acid value-imparting agentwere added to the above monomer dispersion liquid, and the mixture wasloaded into the above dispersion medium system. The resultant wassubjected to a granulating step with the high-speed stirring device for5 minutes while the number of revolutions was maintained at 15,000revolutions/min. After that, the resultant was polymerized for 12 hourswith a propeller stirring blade used as a stirring machine instead ofthe high-speed stirring device at 150 revolutions/min. The resultant washeated to 70° C., and was stirred for 5 hours while the pressure in thecontainer was reduced to 50 kPa. Then, toluene was removed bydistillation. After that, the remainder was cooled to 30° C. at acooling rate of 4.5° C./min. The resultant was filtrated, washed, dried,and classified, whereby toner particles were obtained.

Above toner particles 100 parts by mass Hydrophobic titanium oxidetreated with n-C₄H₉Si(OCH₃)₃ (BET specific surface area: 120 m²/g)

-   -   1 part by mass        Hydrophobic silica treated with hexamethyldisilazane and then        with silicone oil (BET specific surface area: 160 m²/g) 1 part        by mass

A mixture composed of the above components was mixed with a Henschelmixer, whereby Cyan Toner 5 was obtained. Tables 5, 6, and 7 show thephysical properties of the toner.

(Resin Production Example 1)

90 parts by mass of a monomer mixture for polyester composed ofcarboxylic acid monomers (terephthalic acid: 29 mol %, isophthalic acid:16 mol %, dodecenylsuccinic anhydride: 3 mol %), alcohol monomers (abisphenol A derivative 1 represented by the following general formula(9) (R: an ethylene group, x+y=2.4): 30 mol %, and a bisphenol Aderivative 2 represented by the general formula (9) (R: a propylenegroup, x+y=2.4): 22 mol %), and an esterification catalyst (tetrastearyltitanate) were loaded into a reaction vessel equipped with a refluxpipe, a stirring machine, a temperature gauge, a nitrogen introducingpipe, a dropping device, and a decompression device. Under a nitrogenatmosphere, the resultant mixture was heated to 150° C.

A vinyl monomer mixture composed of 8.0 parts by mass of styrene, 1.9parts by mass of 2-ethylhexyl acrylate, 0.1 part by mass of acrylicacid, and 0.1 part by mass of di-t-butyl peroxide was dropped over 2hours while the resultant in the reaction vessel was stirred. Theresultant mixture was heated to 220° C. under reduced pressure so as tobe subjected to a dehydration condensation reaction for 8 hours. Theresultant reaction liquid was charged into 400 parts by mass ofmethanol, and the solid content was collected and dried, whereby a resin1 was obtained. The resultant resin 1 had a number average molecularweight of 5,300, a weight-average molecular weight of 21,600, a glasstransition temperature of 53.8° C., and an acid value of 8.7 mgKOH/g.

(Resin Production Example 2)

100 parts by mass of a monomer mixture for polyester composed ofcarboxylic acid monomers (terephthalic acid: 23 mol %, isophthalic acid:22 mol %, dodecenylsuccinic anhydride: 3 mol %), alcohol monomers (abisphenol A derivative 1 represented by the above general formula (9)(R: an ethylene group, x+y=2.4): 15 mol %, and a bisphenol A derivative2 represented by the general formula (9) (R: a propylene group,x+y=2.4): 35 mol %), and an esterification catalyst (tetrastearyltitanate) were loaded into a reaction vessel equipped with a refluxpipe, a stirring machine, a temperature gauge, a nitrogen introducingpipe, a dropping device, and a decompression device. Under a nitrogenatmosphere, the pressure in the vessel was reduced, and the resultantmixture was heated to 190° C. so as to be subjected to a dehydrationcondensation reaction for 8 hours. The resultant reaction liquid wascharged into 400 parts by mass of methanol, and the solid content wascollected and dried, whereby a resin 2 was obtained. The resultant resin2 had a number average molecular weight of 2,600, a weight-averagemolecular weight of 39,400, a glass transition temperature of 51.3° C.,and an acid value of 17.6 mgKOH/g.

(Resin Production Example 3)

100 parts by mass of a monomer mixture for polyester composed ofcarboxylic acid monomers (terephthalic acid: 22 mol %, trimellitic acid:7 mol %, dodecenylsuccinic anhydride: mol %), alcohol monomers (abisphenol A derivative 1 represented by the above general formula (9)(R: an ethylene group, x+y=2.4): 14 mol %, and a bisphenol A derivative2 represented by the general formula (9) (R: a propylene group,x+y=2.4): 37 mol %), and an esterification catalyst (dibutyltin oxide)were loaded into a reaction vessel equipped with a reflux pipe, astirring machine, a temperature gauge, a nitrogen introducing pipe, adropping device, and a decompression device. Under a nitrogenatmosphere, the pressure in the vessel was reduced, and the resultantmixture was heated to 220° C. so as to be subjected to a dehydrationcondensation reaction for 8 hours, whereby a resin 3 was obtained. Theresultant resin 3 had a number average molecular weight of 43,700, aweight-average molecular weight of 103,600, a glass transitiontemperature of 54.1° C., and an acid value of 0.9 mgKOH/g.

(Wax Dispersant Master Batch Production Example 1)

600 parts by mass of xylene and 120 parts by mass of polyethylene(weight-average molecular weight: 11,000, number average molecularweight: 4,200, highest endothermic peak: 92° C.) were loaded into anautoclave reaction tank mounted with a temperature gauge and a stirringmachine. Under a nitrogen atmosphere, the temperature of the mixture wasincreased to 150° C., and a mixed solution of 1,000 parts by mass ofstyrene, 84 parts by mass of acrylonitrile, 120 parts by mass ofmonobutyl maleate, 40 parts by mass ofdi-t-butylperoxyhexahydrophthalate, and 400 parts by mass of xylene wasdropped to the mixture over 3 hours. Further, the resultant mixture waspolymerized while its temperature was retained at the temperature for 60minutes. Next, xylene was removed by distillation, whereby a waxdispersion medium as a graft reaction product was obtained.

A mixture composed of 25 parts by mass of the resin 1, 25 parts by massof the above wax dispersion medium, and 50 parts by mass of the wax 1shown in Table 1 was sufficiently mixed with a Henschel mixer, and themixture was melted and kneaded with a biaxial extruder. After havingbeen cooled, the kneaded product was coarsely pulverized with a hammermill, whereby a wax dispersant master batch 1 containing a waxdispersant was obtained.

(Wax Dispersant Master Batch Production Examples 2 and 3)

Wax dispersant master batches 2 and 3 were each obtained in the samemanner as in Wax Dispersant Master Batch Production Example 1 exceptthat the wax 1 shown in Table 1 was changed to a wax 2 or 3.

(Colorant-dispersed Body Production Example 1)

40 parts by mass of the resin 1, 100 parts by mass of Pigment Blue 15:3,and 200 parts by mass of xylene were loaded into an Attritor(manufactured by MITSUI MINING & SMELTING CO., LTD.) containing zirconiabeads each having a diameter of 20 mm, and the mixture was rotated at anumber of revolutions of 300 revolutions/min for 8 hours. The zirconiabeads were separated, and xylene was removed by distillation. Afterhaving been cooled, the resultant was coarsely pulverized with a hammermill, and was then finely pulverized with an air-jet pulverizer, wherebya pre-dispersed body 1 was obtained.

Next, 100 parts by mass of the resin 1 and 140 parts by mass of thepre-dispersed body 1 were preliminarily mixed with a Henschel mixer to asufficient extent, and then the mixture was melted and kneaded underheat with a kneader type mixer at 130° C. for 1 hour. After having beencooled, the resultant was coarsely pulverized with a hammer mill, andwas then finely pulverized with an air-jet pulverizer, whereby acolorant-dispersed body 1 was obtained.

(Colorant-dispersed Body Production Examples 2 to 4)

Colorant-dispersed bodies 2 to 4 were each obtained in the same manneras in Colorant-dispersed Body Production Example 1 except that thecolorant in Colorant-dispersed Body Production Example 1 was changed toa colorant shown in Table 2.

(Cyan Toner Production Example 6)

Resin 1 74.8 parts by mass Colorant-dispersed body 1 31.2 parts by mass(colorant content: 12 parts by mass) Wax dispersant master batch 2 12.0parts by mass (the content of the wax 2: 6.0 parts by mass) Sulfonicacid compound 2 1.6 parts by mass Aluminum salicylate compound 1.0 partby mass (BONTRON E-88: manufactured by Orient Chemical Industries, LTD.)

The above materials were preliminarily mixed with a Henschel mixer to asufficient extent, and then the mixture was melted and kneaded with abiaxial extruder. After having been cooled, the resultant was coarselypulverized with a cutter mill, and was then pulverized with an air-jetpulverizer, whereby pulverized products were obtained.

The above pulverized products were subjected to surface modificationwith the apparatus shown in FIG. 7, whereby toner particles wereobtained. A cycle time in this case was set to 30 seconds.

Above toner particles 100 parts by mass Hydrophobic titanium oxidetreated with n-C₄H₉Si(OCH₃)₃ (BET specific surface area: 120 m²/g)

-   -   1 part by mass        Hydrophobic silica treated with hexamethyldisilazane and then        with silicone oil (BET specific surface area: 160 m²/g) 1 part        by mass

The above components were mixed with a Henschel mixer, whereby CyanToner 6 was obtained. Tables 5, 6, and 7 show the physical properties ofthe toner.

(Cyan Toner Production Examples 7 and 10)

Cyan Toners 7 and 10 were each obtained in the same manner as in CyanToner Production Example 6 except that conditions in Cyan TonerProduction Example 6 were changed as shown in Table 4. Tables 5, 6, and7 show the physical properties of the toners.

(Cyan Toner Production Example 8)

Resin 1 81.0 parts by mass Colorant used in Colorant-dispersed body113.0 parts by mass Wax dispersant master batch 2 12.0 parts by mass(the content of the wax 2: 6.0 parts by mass) Aluminum salicylatecompound 1.0 part by mass (BONTRON E-88: manufactured by Orient ChemicalIndustries, LTD.) Sulfonic acid compound 2 1.6 parts by mass

The above materials were preliminarily mixed with a Henschel mixer to asufficient extent, and then the mixture was melted and kneaded with abiaxial extruder. After having been cooled, the resultant was coarselypulverized with a cutter mill, and was then pulverized with an air-jetpulverizer, whereby pulverized products were obtained.

The subsequent operation was the same as that in Cyan Toner ProductionExample 6 except that the cycle time was changed to 45 seconds, wherebyCyan Toner 8 was obtained. Tables 5, 6, and 7 show the physicalproperties of the toner.

(Cyan Toner Production Example 9)

Cyan Toner 9 was obtained in the same manner as in Cyan Toner ProductionExample 8 except that conditions in Cyan Toner Production Example 8 werechanged as shown in Table 4. Tables 5, 6, and 7 show the physicalproperties of the toners.

(Magenta Toner Production Examples 1 to 4, Yellow Toner ProductionExamples 1 to 4, and Black Toner Production Examples 1 to 4)

Magenta Toners 1 to 4 were each obtained in the same manner as in CyanToner Production Example 1 except that conditions in Cyan TonerProduction Example 1 were changed as shown in Tables 2 and 3. Tables 8,9, and 10 show the physical properties of the toners.

Yellow Toners 1 to 4 were each obtained in the same manner as in CyanToner Production Example 1 except that conditions in Cyan TonerProduction Example 1 were changed as shown in Tables 2 and 3. Tables 11,12, and 13 show the physical properties of the toners.

Black Toners 1 to 4 were each obtained in the same manner as in CyanToner Production Example 1 except that conditions in Cyan TonerProduction Example 1 were changed as shown in Tables 2 and 3. Tables 14,15, and 16 show the physical properties of the toners.

(Magenta Toner Production Example 5, Yellow Toner Production Example 5,and Black Toner Production Examples 5 and 6)

Magenta Toner 5 was obtained in the same manner as in Cyan TonerProduction Example 5 except that conditions in Cyan Toner ProductionExample 5 were changed as shown in Tables 2 and 3. Tables 8, 9, and 10show the physical properties of the toners.

Yellow Toner 5 was obtained in the same manner as in Cyan TonerProduction Example 5 except that conditions in Cyan Toner ProductionExample 5 were changed as shown in Tables 2 and 3. Tables 11, 12, and 13show the physical properties of the toners.

Black Toners 5 and 6 was obtained in the same manner as in Cyan TonerProduction Example 5 except that conditions in Cyan Toner ProductionExample 5 were changed as shown in Tables 2 and 3. Tables 14, 15, and 16show the physical properties of the toners.

(Magenta Toner Production Examples 6, 7, and 10, Yellow Toner ProductionExamples 6, 7, and 10, and Black Toner Production Examples 7, 8, and 11)

Magenta Toners 6, 7, and 10 were each obtained in the same manner as inCyan Toner Production Example 6 except that conditions in Cyan TonerProduction Example 6 were changed as shown in Table 4. Tables 8, 9, and10 show the physical properties of the toners.

Yellow Toners 6, 7, and 10 were each obtained in the same manner as inCyan Toner Production Example 6 except that conditions in Cyan TonerProduction Example 6 were changed as shown in Table 4. Tables 11, 12,and 13 show the physical properties of the toners.

Black Toners 7, 8, and 11 were each obtained in the same manner as inCyan Toner Production Example 6 except that conditions in Cyan TonerProduction Example 6 were changed as shown in Table 4. Tables 14, 15,and 16 show the physical properties of the toners.

(Magenta Toner Production Examples 8 and 9, Yellow Toner ProductionExamples 8 and 9, and Black Toner Production Examples 9 and 10)

Magenta Toners 8 and 9 were each obtained in the same manner as in CyanToner Production Example 8 except that conditions in Cyan TonerProduction Example 8 were changed as shown in Tables 4. Tables 8, 9, and10 show the physical properties of the toners.

Yellow Toners 8 and 9 were each obtained in the same manner as in CyanToner Production Example 8 except that conditions in Cyan TonerProduction Example 8 were changed as shown in Table 4. Tables 11, 12,and 13 show the physical properties of the toners.

Black Toners 9 and 10 were each obtained in the same manner as in CyanToner Production Example 8 except that conditions in Cyan TonerProduction Example 8 were changed as shown in Table 4. Tables 14, 15,and 16 show the physical properties of the toners.

TABLE 1 Half width of Highest highest endothermic endothermic Kind ofwax peak peak Mp Mw Mn Wax Refined normal 510 510 410 1 paraffin  78.1°C.  3.2° C. Wax Refined 800 890 610 2 Fischer-Tropsch  91.6° C.  6.4° C.Wax Polyethylene 116.4° C. 21.4 v 2730 8930 1040 3

TABLE 2 Colorant used Cyan toner Pigment Blue 15:3 Production Examples 1to 5 Cyan toner Pigment Blue 15:3 Used in Production Examplescolorant-dispersed 6 to 10 body 1 Magenta toner Mixture containingPigment Production Examples Red 122 and Pigment Red 1 to 5 57:1 in equalamounts Magenta toner Mixture containing Pigment Used in ProductionExamples Red 122 and Pigment Red colorant-dispersed 6 to 10 57:1 inequal amounts body 2 Yellow toner Pigment yellow 140 Production Examples1 to 5 Yellow toner Pigment yellow 74 Used in Production Examplescolorant-dispersed 6 to 10 body 3 Black toner Carbon black ProductionExamples 1 to 5 Black toner Mixture containing carbon Used in ProductionExamples black, Pigment Blue 15:3, colorant-dispersed 6 to 10 PigmentRed 122, and body 4 Pigment Yellow 74 in equal amounts

TABLE 3 Addition amount of Addition amount of Addition amount ofcolorant tricalcium saturated Addition amount of (part(s) by phosphate(part(s) polyester (part(s) sulfonic acid compound Production ExampleToner mass) by mass) by mass) (part(s) by mass) Cyan toner Cyan toner 112 3.5 25.0 1.8 Production Example 1 Cyan toner Cyan toner 2 16 4.0 3.02.4 Production Example 2 Cyan toner Cyan toner 3 9 3.0 25.0 1.2Production Example 3 Cyan toner Cyan toner 4 6 3.5 3.0 — ProductionExample 4 Cyan toner Cyan toner 5 12 3.5 3.0 1.6 Production Example 5Magenta toner Magenta toner 1 12 3.5 25.0 1.8 Production Example 1Magenta toner Magenta toner 2 16 4.0 3.0 2.4 Production Example 2Magenta toner Magenta toner 3 9 3.0 25.0 1.2 Production Example 3Magenta toner Magenta toner 4 6 3.5 3.0 — Production Example 4 Magentatoner Magenta toner 5 12 3.5 3.0 1.6 Production Example 5 Yellow tonerYellow toner 1 12 3.5 25.0 1.8 Production Example 1 Yellow toner Yellowtoner 2 16 4.0 3.0 2.4 Production Example 2 Yellow toner Yellow toner 39 3.0 25.0 1.2 Production Example 3 Yellow toner Yellow toner 4 6 3.53.0 — Production Example 4 Yellow toner Yellow toner 5 12 3.5 3.0 1.6Production Example 5 Black toner Black toner 1 12 3.5 25.0 2.5Production Example 1 Black toner Black toner 2 16 4.0 3.0 3.4 ProductionExample 2 Black toner Black toner 3 9 3.0 25.0 1.7 Production Example 3Black toner Black toner 4 6 3.5 3.0 — Production Example 4 Black tonerBlack toner 5 12 3.5 3.0  2.24 Production Example 5 Black toner Blacktoner 6 16 4.0 3.0  3.36 Production Example 6 Addition PolymerizationAddition amount amount of DSAP Temperature to which temperature of TBEH(part(s) by resultant is heated and Production Example Toner (° C.)(part(s) by mass) mass) time in decompression step Cyan toner Cyan toner1 70 2 1 90° C. for 2 hours Production Example 1 Cyan toner Cyan toner 270 2 1 80° C. for 3 hours Production Example 2 Cyan toner Cyan toner 380 2 1 80° C. for 3 hours Production Example 3 Cyan toner Cyan toner 470 2 1 80° C. for 3 hours Production Example 4 Cyan toner Cyan toner 580 4 1 70° C. for 5 hours Production Example 5 Magenta toner Magentatoner 1 70 2 1 90° C. for 2 hours Production Example 1 Magenta tonerMagenta toner 2 70 2 1 80° C. for 3 hours Production Example 2 Magentatoner Magenta toner 3 80 2 1 80° C. for 3 hours Production Example 3Magenta toner Magenta toner 4 70 2 1 80° C. for 3 hours ProductionExample 4 Magenta toner Magenta toner 5 80 4 1 70° C. for 5 hoursProduction Example 5 Yellow toner Yellow toner 1 70 2 1 90° C. for 2hours Production Example 1 Yellow toner Yellow toner 2 70 2 1 80° C. for3 hours Production Example 2 Yellow toner Yellow toner 3 80 2 1 80° C.for 3 hours Production Example 3 Yellow toner Yellow toner 4 70 2 1 80°C. for 3 hours Production Example 4 Yellow toner Yellow toner 5 80 4 170° C. for 5 hours Production Example 5 Black toner Black toner 1 70 2 190° C. for 2 hours Production Example 1 Black toner Black toner 2 70 2 180° C. for 3 hours Production Example 2 Black toner Black toner 3 80 2 180° C. for 3 hours Production Example 3 Black toner Black toner 4 70 2 180° C. for 3 hours Production Example 4 Black toner Black toner 5 80 4 170° C. for 5 hours Production Example 5 Black toner Black toner 6 70 2 180° C. for 3 hours Production Example 6

TABLE 4 Binder resin Colorant Addition Addition Addition amount ofcolorant Addition amount amount amount with respect to 100 parts by ofsulfonic acid (part(s) (part(s) mass of binder resin compound ProductionExample Toner Kind by mass) Kind by mass (part(s) by mass) (part(s) bymass) Cyan toner Cyan Resin 1 74.8 Colorant-dispersed body 1 31.2 12 1.6Production Example 6 toner 6 Cyan toner Cyan Resin 1 82.8Colorant-dispersed body 1 19.2 8 1.0 Production Example 7 toner 7 Cyantoner Cyan Resin 1 81.0 Colorant used in 13.0 12 1.6 Production Example8 toner 8 colorant-dispersed body 1 Cyan toner Cyan Resin 2 85.0Colorant used in 9.0 8 1.0 Production Example 9 toner 9colorant-dispersed body 1 Cyan toner Cyan Resin 3 63.2Colorant-dispersed body 1 52.8 22 4.5 Production Example 10 toner 10Magenta toner Magenta Resin 1 74.8 Colorant-dispersed body 2 31.2 12 1.6Production Example 6 toner 6 Magenta toner Magenta Resin 1 82.8Colorant-dispersed body 2 19.2 8 1.0 Production Example 7 toner 7Magenta toner Magenta Resin 1 81.0 Colorant used in 13.0 12 1.6Production Example 8 toner 8 colorant-dispersed body 2 Magenta tonerMagenta Resin 2 85.0 Colorant used in 9.0 8 1.0 Production Example 9toner 9 colorant-dispersed body 2 Magenta toner Magenta Resin 3 63.2Colorant-dispersed body 2 52.8 22 4.5 Production Example 10 toner 10Yellow toner Yellow Resin 1 74.8 Colorant-dispersed body 3 31.2 12 1.6Production Example 6 toner 6 Yellow toner Yellow Resin 1 82.8Colorant-dispersed body 3 19.2 8 1.0 Production Example 7 toner 7 Yellowtoner Yellow Resin 1 81.0 Colorant used in 13.0 12 1.6 ProductionExample 8 toner 8 colorant-dispersed body 3 Yellow toner Yellow Resin 285.0 Colorant used in 9.0 8 1.0 Production Example 9 toner 9colorant-dispersed body 3 Yellow toner Yellow Resin 3 63.2Colorant-dispersed body 3 52.8 22 4.5 Production Example 10 toner 10Black toner Black Resin 1 74.8 Colorant-dispersed body 4 31.2 12 1.6Production Example 7 toner 7 Black toner Black Resin 1 82.8Colorant-dispersed body 4 19.2 8 1.0 Production Example 8 toner 8 Blacktoner Black Resin 1 81.0 Colorant used in 13.0 12 1.6 Production Example9 toner 9 colorant-dispersed body 4 Black toner Black Resin 2 85.0Colorant used in 9.0 8 1.0 Production Example 10 toner 10colorant-dispersed body 4 Black toner Black Resin 3 63.2Colorant-dispersed body 4 52.8 22 4.5 Production Example 11 toner 11 WaxAddition amount of colorant with Addition amount respect to 100 parts bymass of Production Example Toner Kind (part(s) by mass) binder resin(part(s) by mass) Cycle time (sec) Cyan toner Cyan Wax dispersant 12 630 Production Example 6 toner 6 master batch 2 Cyan toner Cyan Waxdispersant 12 6 45 Production Example 7 toner 7 master batch 2 Cyantoner Cyan Wax dispersant 12 6 45 Production Example 8 toner 8 masterbatch 2 Cyan toner Cyan Wax dispersant 12 6 15 Production Example 9toner 9 master batch 2 Cyan toner Cyan Wax dispersant 12 6 15 ProductionExample 10 toner 10 master batch 3 Magenta toner Magenta Wax dispersant12 6 30 Production Example 6 toner 6 master batch 2 Magenta tonerMagenta Wax dispersant 12 6 45 Production Example 7 toner 7 master batch2 Magenta toner Magenta Wax dispersant 12 6 45 Production Example 8toner 8 master batch 2 Magenta toner Magenta Wax dispersant 12 6 15Production Example 9 toner 9 master batch 2 Magenta toner Magenta Waxdispersant 12 6 15 Production Example 10 toner 10 master batch 3 Yellowtoner Yellow Wax dispersant 12 6 30 Production Example 6 toner 6 masterbatch 2 Yellow toner Yellow Wax dispersant 12 6 45 Production Example 7toner 7 master batch 2 Yellow toner Yellow Wax dispersant 12 6 45Production Example 8 toner 8 master batch 2 Yellow toner Yellow Waxdispersant 12 6 15 Production Example 9 toner 9 master batch 2 Yellowtoner Yellow Wax dispersant 12 6 15 Production Example 10 toner 10master batch 3 Black toner Black Wax dispersant 12 6 30 ProductionExample 7 toner 7 master batch 2 Black toner Black Wax dispersant 12 645 Production Example 8 toner 8 master batch 2 Black toner Black Waxdispersant 12 6 45 Production Example 9 toner 9 master batch 2 Blacktoner Black Wax dispersant 12 6 15 Production Example 10 toner 10 masterbatch 2 Black toner Black Wax dispersant 12 6 15 Production Example 11toner 11 master batch 3

TABLE 5 Shape Thermal properties Content of Content of particlesparticles each each having a having a particle particle Half widthdiameter diameter one Highest of highest True twice or more half or lessas Standard endo- endo- Endo- Production density D4 as large as D4 largeD1 Average deviation of Tg thermic thermic therm Example Toner ρ (μm)D4/D1 (wt %) (numbers) circularity circularities (° C.) peak (° C.) peak(° C.) (J/cm³) Cyan toner Cyan 1.10 4.2 1.12 2.3 3.4 0.983 0.012 51.677.8 3.2 9.3 Production toner 1 Example 1 Cyan toner Cyan 1.10 3.6 1.165.4 11.2 0.973 0.017 50.8 77.8 3.2 9.3 Production toner 2 Example 2 Cyantoner Cyan 1.10 4.8 1.18 4.8 6.3 0.974 0.018 51.4 77.8 3.2 9.3Production toner 3 Example 3 Cyan toner Cyan 1.10 4.2 1.18 6.1 7.4 0.9570.031 50.9 77.8 3.2 9.3 Production toner 4 Example 4 Cyan toner Cyan1.10 4.2 1.19 6.8 13.7 0.954 0.033 50.2 77.8 3.2 9.3 Production toner 5Example 5 Cyan toner Cyan 1.24 5.3 1.18 3.5 4.9 0.967 0.026 54.2 91.56.3 7.2 Production toner 6 Example 6 Cyan toner Cyan 1.24 5.3 1.23 4.25.1 0.956 0.032 54.1 91.5 6.3 7.2 Production toner 7 Example 7 Cyantoner Cyan 1.24 5.3 1.23 4.6 5.2 0.957 0.031 54.3 91.5 6.3 7.2Production toner 8 Example 8 Cyan toner Cyan 1.24 5.3 1.33 5.7 7.8 0.9340.047 53.9 91.5 6.3 7.2 Production toner 9 Example 9 Cyan toner Cyan1.24 7.6 1.33 15.3 21.6 0.933 0.051 55.4 116.2 21.2 3.9 Production toner10 Example 10 Molecular weight Content of Content of component havingcomponent having Content of molecular weight molecular weightTHF-soluble Production of 3,000 to 5,000 of 300 to 800 component ExampleToner Mw Mn Mw/Mn (mass %) (mass %) (mass %) Cyan toner Cyan 97100 780012.4 15.7 4.2 91.3 Production toner 1 Example 1 Cyan toner Cyan 972007700 12.6 15.8 4.3 91.2 Production toner 2 Example 2 Cyan toner Cyan25300 6300 4.0 15.9 4.2 91.4 Production toner 3 Example 3 Cyan tonerCyan 97100 7700 12.6 15.7 4.2 91.3 Production toner 4 Example 4 Cyantoner Cyan 14800 3200 4.6 43.2 7.1 97.2 Production toner 5 Example 5Cyan toner Cyan 29300 6200 4.7 15.8 3.7 86.6 Production toner 6 Example6 Cyan toner Cyan 29400 6100 4.8 15.9 3.8 86.7 Production toner 7Example 7 Cyan toner Cyan 29200 6200 4.7 15.7 3.9 86.8 Production toner8 Example 8 Cyan toner Cyan 47600 2900 16.4 43.2 10.4 91.3 Productiontoner 9 Example 9 Cyan toner Cyan 135400 67100 2.0 4.6 0.3 97.9Production toner 10 Example 10

TABLE 6 Melt properties Reflection spectral characteristics Softeningpoint η_(C105)/ A_(C620)/ A_(C710)/ Toner (° C.) η_(C105) η_(C120)η_(C20) A_(C620) A_(C470) A_(C670) A_(C670) A_(C420) A_(C670) h*_(C)L*_(C) C*_(C) Cyan toner 1 96 11800 1300 9.1 1.91 0.165 1.08 1.761 0.4511.05 245.5 46.2 66.4 Cyan toner 2 88 6280 540 12.6 2.05 0.179 1.06 1.9270.491 1.04 247.5 44.1 66.9 Cyan toner 3 94 10400 600 17.3 1.74 0.1581.09 1.604 0.429 1.05 244.8 47.8 65.3 Cyan toner 4 92 6810 530 12.8 1.340.124 1.09 1.226 0.325 1.11 237.0 56.2 61.3 Cyan toner 5 73 4200 90 46.71.77 0.290 0.97 1.816 0.674 0.96 429.9 38.7 58.7 Cyan toner 6 109 248002700 9.2 1.88 0.166 1.08 1.743 0.453 1.05 245.7 46.2 66.2 Cyan toner 7109 24700 2600 9.5 1.59 0.112 1.15 1.388 0.309 1.13 235.1 55.7 65.5 Cyantoner 8 108 24700 2700 9.1 1.78 0.257 0.98 1.812 0.601 0.97 246.3 41.360.3 Cyan toner 9 86 6830 320 21.3 1.29 0.141 1.07 1.205 0.343 1.09236.5 55.6 58.7 Cyan toner 10 122 68300 15800 4.3 1.76 0.362 0.97 1.8060.840 0.97 257.1 33.6 55.4

TABLE 7 Acid Content of value A_(C)1 Sulfonic acid sulfur element Toner(mg KOH/g) A_(C)1-A_(C)2 compound (mass %) Cyan toner 1 12.4 8.5Sulfonic acid 0.072 compound 1 Cyan toner 2 6.3 2.5 Sulfonic acid 0.096compound 1 Cyan toner 3 11.9 8.1 Sulfonic acid 0.048 compound 1 Cyantoner 4 1.3 0.2 — 0.000 Cyan toner 5 4.6 0.8 Sulfonic acid 0.064compound 1 Cyan toner 6 7.2 1.6 Sulfonic acid 0.057 compound 2 Cyantoner 7 6.4 0.9 Sulfonic acid 0.039 compound 2 Cyan toner 8 7.1 1.5Sulfonic acid 0.063 compound 2 Cyan toner 9 2.1 0.4 Sulfonic acid 0.038compound 2 Cyan toner 10 32.1 15.6 Sulfonic acid 0.176 compound 2

TABLE 8 Shape Thermal properties Content of Content of Half particlesparticles each width each having a having a of particle particle Highesthighest diameter diameter one endo- endo- True twice or more half orless as Standard thermic thermic Endo- Production density D4 as large asD4 large D1 Average deviation of Tg peak peak therm Example Toner ρ (μm)D4/D1 (wt %) (numbers) circularity circularities (° C.) (° C.) (° C.)(J/cm³) Magenta toner Magenta 1.10 4.2 1.11 2.2 3.3 0.984 0.011 51.577.8 3.2 9.3 Production toner 1 Example 1 Magenta toner Magenta 1.10 3.61.15 5.3 11.1 0.975 0.016 50.8 77.8 3.2 9.3 Production toner 2 Example 2Magenta toner Magenta 1.10 4.8 1.18 4.7 6.2 0.974 0.017 51.3 77.8 3.29.3 Production toner 3 Example 3 Magenta toner Magenta 1.10 4.2 1.18 6.07.4 0.958 0.030 50.9 77.8 3.2 9.3 Production toner 4 Example 4 Magentatoner Magenta 1.10 4.2 1.18 6.8 13.6 0.954 0.032 50.2 77.8 3.2 9.3Production toner 5 Example 5 Magenta toner Magenta 1.24 5.3 1.19 3.5 4.80.968 0.025 54.1 91.5 6.3 7.2 Production toner 6 Example 6 Magenta tonerMagenta 1.24 5.3 1.22 4.1 5.0 0.957 0.031 54.1 91.5 6.3 7.2 Productiontoner 7 Example 7 Magenta toner Magenta 1.24 5.3 1.22 4.6 5.2 0.9580.030 54.2 91.5 6.3 7.2 Production toner 8 Example 8 Magenta tonerMagenta 1.24 5.3 1.32 5.6 7.7 0.933 0.046 53.9 91.5 6.3 7.2 Productiontoner 9 Example 9 Magenta toner Magenta 1.24 7.6 1.32 15.2 21.5 0.9340.051 55.3 116.2 21.2 3.9 Production toner 10 Example 10 Molecularweight Content of Content of component having component having Contentof molecular weight molecular weight THF-soluble Production of 3,000 to5,000 of 300 to 800 component Example Toner Mw Mn Mw/Mn (mass %) (mass%) (mass %) Magenta toner Magenta 97200 7800 12.5 15.7 4.2 91.2Production toner 1 Example 1 Magenta toner Magenta 97100 7700 12.6 15.84.1 91.3 Production toner 2 Example 2 Magenta toner Magenta 25100 62004.0 16.0 4.2 91.5 Production toner 3 Example 3 Magenta toner Magenta97100 7700 12.6 15.7 4.2 91.3 Production toner 4 Example 4 Magenta tonerMagenta 14700 3200 4.6 43.1 7.2 97.3 Production toner 5 Example 5Magenta toner Magenta 29400 6200 4.7 15.7 3.6 86.7 Production toner 6Example 6 Magenta toner Magenta 29300 6200 4.7 15.8 3.7 86.6 Productiontoner 7 Example 7 Magenta toner Magenta 29300 6100 4.8 15.8 3.8 86.8Production toner 8 Example 8 Magenta toner Magenta 47500 2860 16.6 43.410.7 86.8 Production toner 9 Example 9 Magenta toner Magenta 13510066900 2.0 4.7 0.2 98.1 Production toner 10 Example 10

TABLE 9 Melt properties Reflection spectral characteristics Softeningpoint η_(M105)/ A_(M)570/ AM570/ Toner (° C.) η_(M105) η_(M120) η_(M120)A_(M)570 A_(M)620 A_(M)450 A_(M)450 A_(M)490 AM550 h*_(M) L*_(M) C*_(M)Magenta toner 1 96 11700 1280 9.1 1.972 0.158 2.51 0.785 1.242 10.3 0.1343.61 79.1 Magenta toner 2 88 6800 530 12.8 2.113 0.167 2.52 0.838 1.3461.00 1.95 42.46 80.09 Magenta toner 3 94 10300 590 17.5 1.904 0.152 2.540.749 1.181 1.04 358.75 44.34 78.64 Magenta toner 4 92 6800 530 12.81.521 0.100 2.78 0.548 0.863 1.08 351.57 50.07 76.26 Magenta toner 5 724180 90 46.4 1.714 0.176 1.57 1.091 1.633 0.94 15.52 43.56 79.74 Magentatoner 6 109 24700 2690 9.2 2.038 0.159 2.61 0.780 1.246 1.02 359.5843.41 79.59 Magenta toner 7 108 24600 2620 9.4 1.670 0.103 2.87 0.5810.924 1.08 352.66 48.65 78.43 Magenta toner 8 108 24700 2640 9.4 1.7490.145 1.70 1.031 1.631 0.94 14.09 44.67 81.36 Magenta toner 9 86 6810300 22.7 1.526 0.220 1.25 1.222 1.549 0.95 20.39 42.79 75.75 Magentatoner 10 121 68100 15600 4.4 1.762 0.294 1.10 1.606 1.870 0.93 27.4838.29 80.01

TABLE 10 Content of Acid value sulfur A_(M)1 Sulfonic acid element Toner(mg KOH/g) A_(M)1-A_(M)2 compound (mass %) Magenta toner 1 12.3 8.4Sulfonic acid 0.071 compound 1 Magenta toner 2 6.3 2.5 Sulfonic acid0.095 compound 1 Magenta toner 3 11.8 8 Sulfonic acid 0.048 compound 1Magenta toner 4 1.3 0.2 — 0.000 Magenta toner 5 4.6 0.8 Sulfonic acid0.063 compound 1 Magenta toner 6 7.1 1.5 Sulfonic acid 0.057 compound 2Magenta toner 7 6.4 0.9 Sulfonic acid 0.039 compound 2 Magenta toner 8 71.4 Sulfonic acid 0.062 compound 2 Magenta toner 9 2.1 0.4 Sulfonic acid0.038 compound 2 Magenta toner 10 31.9 15.4 Sulfonic acid 0.174 compound2

TABLE 11 Shape Thermal properties Content of Content of Half particlesparticles each width each having a having a of particle particle Highesthighest diameter diameter one endo- endo- True twice or more half orless as Standard thermic thermic Endo- Production density D4 as large asD4 large D1 Average deviation of Tg peak- peak therm Example Toner ρ(μm) D4/D1 (wt %) (numbers) circularity circularities (° C.) (° C.) (°C.) (J/cm³) Yellow toner Yellow 1.10 4.3 1.13 2.4 3.5 0.982 0.013 51.777.8 3.2 9.3 Production toner 1 Example 1 Yellow toner Yellow 1.10 3.71.16 5.5 11.3 0.972 0.017 50.8 77.8 3.2 9.3 Production toner 2 Example 2Yellow toner Yellow 1.10 4.9 1.19 4.9 6.4 0.973 0.019 51.5 77.8 3.2 9.3Production toner 3 Example 3 Yellow toner Yellow 1.10 4.3 1.19 6.2 7.50.956 0.032 51.0 77.8 3.2 9.3 Production toner 4 Example 4 Yellow tonerYellow 1.10 4.3 1.20 6.9 13.8 0.953 0.034 50.3 77.8 3.2 9.3 Productiontoner 5 Example 5 Yellow toner Yellow 1.24 5.4 1.19 3.6 4.9 0.966 0.02554.3 91.5 6.3 7.2 Production toner 6 Example 6 Yellow toner Yellow 1.245.4 1.23 4.3 5.2 0.955 0.032 54.2 91.5 6.3 7.2 Production toner 7Example 7 Yellow toner Yellow 1.24 5.4 1.23 4.7 5.3 0.958 0.032 54.391.5 6.3 7.2 Production toner 8 Example 8 Yellow toner Yellow 1.24 5.41.34 5.8 7.9 0.932 0.048 54.0 91.5 6.3 7.2 Production toner 9 Example 9Yellow toner Yellow 1.24 7.6 1.34 15.4 21.8 0.932 0.052 55.4 116.2 21.23.9 Production toner 10 Example 10 Molecular weight Content of Contentof component having component having Content of molecular weightmolecular weight THF-soluble Production of 3,000 to 5,000 of 300 to 800component Example Toner Mw Mn Mw/Mn (mass %) (mass %) (mass %) Yellowtoner Yellow 97300 7900 12.3 15.6 4.1 91.2 Production toner 1 Example 1Yellowa toner Yellow 97400 7800 12.5 15.7 4.2 91.2 Production toner 2Example 2 Yellow toner Yellow 25400 6400 4.0 16.0 4.1 91.3 Productiontoner 3 Example 3 Yellowa toner Yellow 97300 7800 12.5 15.5 4.0 91.2Production toner 4 Example 4 Yellow toner Yellow 14900 3300 4.5 43.1 6.997.1 Production toner 5 Example 5 Yellow toner Yellow 29400 6300 4.715.7 3.7 86.6 Production toner 6 Example 6 Yellow toner Yellow 295006100 4.8 15.8 3.8 86.6 Production toner 7 Example 7 Yellow toner Yellow29300 6200 4.7 15.7 3.8 86.7 Production toner 8 Example 8 Yellow tonerYellow 47700 2890 16.5 43.1 10.3 86.6 Production toner 9 Example 9Yellow toner Yellow 135800 67300 2.0 4.5 0.1 97.7 Production toner 10Example 10

TABLE 12 Melt properties Reflection spectral characteristics Softeningpoint η_(Y105)/ A_(Y470/) Toner (° C.) η_(Y105) η_(Y120) η_(Y120)A_(Y)450 A_(Y)470 A_(Y)510 A_(Y490) h*_(Y) L*_(Y) C*_(Y) Yellow toner 197 11900 1320 9.0 1.852 1.767 0.241 1.49 93.20 92.48 113.45 Yellow toner2 89 6850 560 12.2 2.046 1.935 0.272 1.46 92.68 92.13 116.73 Yellowtoner 3 94 10600 620 17.1 1.745 1.669 0.232 1.48 93.38 92.35 110.99Yellow toner 4 92 6820 540 12.6 1.560 1.433 0.126 1.97 95.89 93.63103.70 Yellow toner 5 73 4220 90 46.9 1.718 1.652 0.535 1.16 87.89 93.37119.13 Yellow toner 6 109 24900 2720 9.2 1.835 1.741 0.245 1.46 93.1792.28 112.89 Yellow toner 7 109 24800 2670 9.3 1.663 1.525 0.134 1.9695.60 93.53 105.28 Yellow toner 8 108 24800 2710 9.2 1.690 1.639 0.6191.13 86.62 92.57 118.74 Yellow toner 9 87 6850 360 19.0 1.627 1.3130.176 1.97 94.08 96.11 106.15 Yellow toner 10 124 68900 16300 4.2 1.7481.683 0.847 1.13 83.73 90.40 119.91

TABLE 13 Content of Acid value sulfur A_(Y)1 Sulfonic acid element Toner(mg KOH/g) A_(Y)1-A_(Y)2 compound (mass %) Yellow toner 1 12.6 8.6Sulfonic acid 0.073 compound 1 Yellow toner 2 6.4 2.6 Sulfonic acid0.097 compound 1 Yellow toner 3 12 8.2 Sulfonic acid 0.048 compound 1Yellow toner 4 1.4 0.3 — 0.000 Yellow toner 5 4.7 0.8 Sulfonic acid0.065 compound 1 Yellow toner 6 7.3 1.7 Sulfonic acid 0.057 compound 2Yellow toner 7 6.4 0.9 Sulfonic acid 0.039 compound 2 Yellow toner 8 7.21.6 Sulfonic acid 0.064 compound 2 Yellow toner 9 2.2 0.5 Sulfonic acid0.038 compound 2 Yellow toner 10 32.3 15.7 Sulfonic acid 0.177 compound2

TABLE 14 Shape Thermal properties Content of Content of Half particlesparticles each width each having a having a of particle particle highestdiameter diameter one endo- True twice or more half or less as StandardHighest thermic Endo- Production density D4 as large as D4 large D1Average deviation of Tg endothermic peak therm Example Toner ρ (μm)D4/D1 (wt %) (numbers) circularity circularities (° C.) peak (° C.) (°C.) (J/cm³) Black toner Black 1.10 4.2 1.11 2.3 3.3 0.984 0.012 51.677.8 3.2 9.3 Production toner 1 Example 1 Black toner Black 1.10 3.61.12 4.8 9.8 0.974 0.016 50.9 77.8 3.2 9.3 Production toner 2 Example 2Black toner Black 1.10 4.7 1.17 4.7 6.2 0.975 0.017 51.5 77.8 3.2 9.3Production toner 3 Example 3 Black toner Black 1.10 4.2 1.18 6.1 7.50.958 0.032 50.9 77.8 3.2 9.3 Production toner 4 Example 4 Black tonerBlack 1.10 4.2 1.19 6.9 13.8 0.955 0.034 50.3 77.8 3.2 9.3 Productiontoner 5 Example 5 Black toner Black 1.24 4.3 1.22 7.1 15.1 0.953 0.03850.2 77.8 3.2 9.3 Production toner 6 Example 6 Black toner Black 1.245.3 1.17 3.4 4.8 0.968 0.025 54.2 91.5 6.3 7.2 Production toner 7Example 7 Black toner Black 1.24 5.3 1.22 4.1 4.9 0.957 0.031 54.2 91.56.3 7.2 Production toner 8 Example 8 Black toner Black 1.24 5.3 1.23 4.75.1 0.956 0.032 54.3 91.5 6.3 7.2 Production toner 9 Example 9 Blacktoner Black 1.24 5.3 1.34 5.8 7.9 0.932 0.049 53.9 91.5 6.3 7.2Production toner 10 Example 10 Black toner Black 1.24 7.5 1.33 15.4 21.70.932 0.052 55.3 116.2 21.2 3.9 Production toner 11 Example 11 Molecularweight Content of Content of component having component having Contentof molecular weight molecular weight THF-soluble Production of 3,000 to5,000 of 300 to 800 component Example Toner Mw Mn Mw/Mn (mass %) (mass%) (mass %) Black toner Black 96900 7600 12.8 16.1 3.9 91.4 Productiontoner 1 Example 1 Black toner Black 97100 7700 12.6 15.9 4.1 91.1Production toner 2 Example 2 Black toner Black 25100 6280 4.0 16.1 4.091.5 Production toner 3 Example 3 Black toner Black 96800 7500 12.9 15.84.1 91.4 Production toner 4 Example 4 Black toner Black 14600 3100 4.743.1 7.2 97.2 Production toner 5 Example 5 Black toner Black 96700 740013.1 15.9 4.0 91.5 Production toner 6 Example 6 Black toner Black 294006300 4.7 15.7 3.6 86.6 Production toner 7 Example 7 Black toner Black29500 6300 4.7 15.8 3.7 86.7 Production toner 8 Example 8 Black tonerBlack 29400 6200 4.7 15.7 3.9 86.7 Production toner 9 Example 9 Blacktoner Black 47700 2910 16.4 43.0 10.5  86.8 Production toner 10 Example10 Black toner Black 136000 66500 2.0 4.4 0.4 97.9 Production toner 11Example 11

TABLE 15 Melt properties Reflection spectral characteristics Softeningpoint η_(K105)/ A_(K)600/ A_(K)460/ Toner (° C.) η_(K105) η_(K120)η_(K120) A_(K)600 A_(K)460 A_(K)460 A_(K)670 A_(K)670 L*_(K) a*_(K)b*_(K) c*_(K) Black toner 1 95 11600 1260 9.2 1.763 1.007 1.751 1.7321.011 14.22 −0.45 −0.09 0.46 Black toner 2 88 6760 520 13.0 1.883 1.0121.861 1.843 1.010 11.64 −0.38 −0.18 0.42 Black toner 3 94 10300 580 17.81.714 0.994 1.725 1.663 1.037 15.52 −1.04 1.12 1.53 Black toner 4 916790 510 13.3 1.577 0.995 1.585 1.529 1.037 19.01 −1.09 1.33 1.72 Blacktoner 5 72 4180 80 52.3 1.639 0.946 1.732 1.593 1.087 16.34 1.13 2.893.11 Black toner 6 94 11500 1250 9.2 1.883 0.957 1.968 1.832 1.074 10.890.95 2.36 2.55 Black toner 7 109 24900 2680 9.3 1.788 1.022 1.749 1.7820.981 13.62 0.04 −1.45 1.45 Black toner 8 109 24800 2640 9.4 1.675 1.0311.624 1.689 0.962 16.47 −0.41 −1.91 1.96 Black toner 9 108 24800 25609.7 1.766 1.040 1.698 1.779 0.954 14.30 −0.33 −2.27 2.30 Black toner 1086 6840 290 23.6 1.643 1.046 1.570 1.663 0.944 17.49 −0.72 −2.42 2.52Black toner 11 124 69200 16100 4.3 1.951 1.037 1.882 1.950 0.965 10.39−0.24 −1.82 1.84

TABLE 16 Content of Acid value sulfur A_(K)1 Sulfonic acid element Toner(mg KOH/g) A_(K)1-A_(K)2 compound (mass %) Black toner 1 12.6 8.6Sulfonic acid 0.072 compound 1 Black toner 2 6.4 2.5 Sulfonic acid 0.096compound 1 Black toner 3 12.1 8.2 Sulfonic acid 0.048 compound 1 Blacktoner 4 1.4 0.3 — 0.000 Black toner 5 4.7 0.8 Sulfonic acid 0.064compound 1 Black toner 6 7.8 3.9 Sulfonic acid 0.152 compound 1 Blacktoner 7 7.4 1.7 Sulfonic acid 0.057 compound 2 Black toner 8 6.5 0.9Sulfonic acid 0.040 compound 2 Black toner 9 7.3 1.6 Sulfonic acid 0.065compound 2 Black toner 10 2.2 0.4 Sulfonic acid 0.039 compound 2 Blacktoner 11 32.4 15.8 Sulfonic acid 0.181 compound 2

(Carrier Production Example 1)

A magnetite powder (Fe₃O₄) having a number average particle diameter of180 nm, an intensity of magnetization of 72 Am²/kg, and a specificresistance of 5.1×10⁵ Ω·cm was calcined in the air at 700° C. for 3hours. 4.2 mass % of a silane coupling agent(3-(2-aminoethylaminopropyl)trimethoxysilane) were added to themagnetite powder. The materials were mixed and stirred in a container at120° C. so that the surface of the above magnetite powder was treated.Thus, a treated magnetite powder was obtained.

Phenol 10 parts by mass Formaldehyde solution (37-mass % aqueoussolution 14 parts by mass of formaldehyde) Magnetite powder subjected tohydrophobic treatment 90 parts by mass

The above materials were sufficiently mixed in a flask. Under a nitrogenatmosphere, 4 parts by mass of 28-mass % ammonia water and 12 parts bymass of water were added to the flask. The mixture was heated whilebeing stirred so that its temperature was retained at 85° C. Then, themixture was subjected to a polymerization reaction for 4 hours so as tobe cured.

After having been cooled to 30° C., the cured product was washed withwater and dried, whereby spherical carrier particles 1 were obtained.

A mixture composed of the following materials was loaded into a reactionvessel equipped with a reflux pipe, a stirring machine, a temperaturegauge, a nitrogen introducing pipe, a dropping device, and adecompression device. The mixture was heated to 70° C. under a nitrogenatmosphere while being stirred, and the temperature was retained for 10hours.

Methyl methacrylate macromonomer (AA-6  10 parts by mass manufactured byTOAGOSEI CO., LTD.) Methyl methacrylate  90 parts by mass Toluene 100parts by mass Methyl ethyl ketone 110 parts by mass2,2′-azobis(2,4-dimethylvaleronitrile)  2.4 parts by mass

2 parts by mass of carbon black (manufactured by Tokai Carbon Co., Ltd.:TOKABLACK #5500) and 200 parts by mass of toluene were added to themixture, and the whole was sufficiently mixed with a homogenizer,whereby a coat liquid was obtained. Subsequently, 100 parts by mass ofthe carrier particles 1 were stirred while a shearing stress wascontinuously applied, and, during the stirring, 25 parts by mass of theabove coat liquid were gradually added. The temperature of the resultantmixture was retained at 70° C., and the mixture was stirred. Further,the temperature was increased to 100° C., and then the mixture wasstirred for 2 hours. After having been cooled, the mixture was shredded.Further, the shredded products were classified, whereby Carrier 1 wasobtained.

Carrier 1 had a 50% particle diameter on a volume basis (D50) of 24.6μm, a true specific gravity of 3.55 g/cm³, an intensity of magnetizationof 64 Am²/kg, and a specific resistance of 2.1×10¹² Ω·cm.

(Carrier Production Example 2)

12.578 mol % of LiO, 6.500 mol % of MgO, 80.600 mol % of Fe₂O₃, 0.020mol % of MnO, and 0.002 mol % of CuO were mixed with a wet ball mill for5 hours, and the mixture was dried. The temperature of the mixture wasretained at 850° C. for 1 hour, and then the mixture was temporarilycalcined. The resultant was pulverized with a wet ball mill for 6 hoursinto particles having a number average particle diameter of 2 μm. 2.4mass % of polyvinyl alcohol were added to the particles. Subsequently,the mixture was granulated and dried with a spray dryer. In an electricfurnace, the temperature of each of the granulated products was retainedat 1,200° C. for 4 hours, and then the granulated products werecalcined. After that, the calcined products were shredded and screenedwith a sieve having an aperture of 250 μm so that coarse particles wereremoved. Thus, carrier particles 2 were obtained.

The subsequent operation was the same as that in Carrier ProductionExample 1 except that the usage of the coat liquid was changed to 18parts by mass, whereby Carrier 2 was obtained.

Carrier 2 had a 50% particle diameter on a volume basis (D50) of 33.6μm, a true specific gravity of 3.69 g/cm³, an intensity of magnetizationof 59 Am²/kg, and a specific resistance of 2.9×10¹² Ω·cm.

Example 1

8 parts by mass of Cyan Toner 1 and 92 parts by mass of Carrier 1 weremixed, whereby a two-component cyan developer 1 was obtained. 8 parts bymass of Magenta Toner 4, Yellow Toner 4, or Black Toner 4 and 92 partsby mass of Carrier 1 were similarly mixed, whereby a two-componentmagenta developer 4, a two-component yellow developer 4, or atwo-component black developer 4 was obtained, respectively.

The two-component cyan developer 1 was set in the cyan developing deviceof a commercially available full-color copying machine (iRC3220,manufactured by Canon Inc.), and the magenta developer 4, yellowdeveloper 4, and black developer 4 described above were set in the otherdeveloping devices of the machine corresponding to the respectivecolors. The two-component cyan developer 1 was designed so that a toneramount to be used in the development of an electrostatic latent imageidentical to a conventional one was small and the charge quantity of thetoner was large. Image data based on a CIELAB color coordinate systemwith (L*=53.9, a*=−37.0, b*=−50.1) (cyan solid image specified as aJapan color) was printed on plain paper (A4-size CLC paper (81.4 g/m²);manufactured by Canon Inc.), and a toner amount M1_(C) (mg/cm²) used inthe development of the image data on the paper was measured.

In addition, the fixing unit of the full-color copying machine (iRC3220;manufactured by Canon Inc.) was removed and reconstructed so that thetemperature of a fixing member could be adjusted, and then a fixabilitytest was performed. The above toner image was fixed under anormal-temperature, normal-humidity environment in the range of 110° C.to 220° C. while the preset temperature of the fixing unit was changedin an increment of 10° C. The temperature at which cold offset was nolonger observed was defined as a low non-offset temperature. Atemperature lower than the lower one of the temperature at which hotoffset was observed and the temperature at which the winding of receiverpaper around the fixing unit occurred by 10° C. was defined as a highnon-offset temperature.

The preset temperature of the fixing unit of the commercially availablefull-color copying machine (iRC3220; manufactured by Canon Inc.) waschanged so as to be lower than the temperature at which average glosswas largest in the above fixability test by 10° C., and thetwo-component cyan developer 1 was set in the cyan developing device ofthe machine. In addition, the two-component magenta developer 4, thetwo-component yellow developer 4, and the two-component black developer4 corresponding to the respective colors were set in the otherdeveloping devices of the machine. A full-color image was formed under anormal-temperature, normal-humidity environment, and a color space wasmeasured. Further, belt-like solid images each measuring 3 cm long by 15cm wide and each created from image data based on a CIELAB colorcoordinate system with (L*=53.9, a*=−37.0, b*=−50.1) (cyan solid imagespecified as a Japan color) and images on each of which 30 circular dotseach having a diameter of 42 μm were formed at an interval of one spacefor one dot were continuously printed. A cyan image on a first sheet, a3,000-th sheet, or a 6,000-th sheet was evaluated for the spread stateof each dot, the chipped state of each dot, and the gloss uniformity ofa solid portion. At that time, part of the cyan developer present on adeveloping sleeve was collected, and the charge quantity of the tonerwas measured. Further, the height of a toner image developed on anelectrostatic image bearing member was measured. Table 18 shows theresults.

Evaluation criteria for the respective items in examples will be shownbelow.

(Color Space)

A full-color image with a 256-step gradation was formed, and its colorspace volume was evaluated as a relative value when the color spacevolume of Comparative Example 1 to be described later was defined as100%.

A: The color space volume is 97% or more of the area of ComparativeExample 1 (color space performance: most excellent).

B: The color space volume is 94% or more and less than 97% of the areaof Comparative Example 1 (color space performance: excellent).

C: The color space volume is 90% or more and less than 94% of the areaof Comparative Example 1 (color space performance: good).

D: The color space volume is less than 90% of the area of ComparativeExample 1 (color space performance: poor).

(Gloss Uniformity)

A difference in gloss between a solid image portion at a front endportion and a solid image portion at a rear end portion was measured forthe direction in which paper was passed.

A: The difference in gloss is less than 5 (gloss uniformity: mostexcellent).

B: The difference in gloss is 5 or more and less than 10 (glossuniformity: excellent).

C: The difference in gloss is 10 or more and less than 15 (glossuniformity: good).

D: The difference in gloss is 15 or more (gloss uniformity: poor).

(Dot Spread)

Dot spread can be measured with a commercially available opticalmicroscope. To be specific, the dot spread can be measured with, forexample, a color laser microscope (VK-9500, manufactured by KEYENCECORPORATION). In a fixed image on which image data on a square solidimage (600 dpi, one dot) measuring 42.3 μm long by 42.3 μm wide isoutput, the area of the square is defined as 100%, and the area of tonerspreading from the square is determined in a percentage unit. The sameoperation was performed for 30 randomly sampled images, and evaluationfor dot spread was performed by determining the average of the areas.Evaluation criteria are shown below. FIG. 13 shows a conceptual view ofdot spread. It should be noted that, for each of a cyan image, a magentaimage, and a yellow image, data on an observed image was divided intored (R), green (G), and blue (B), and the cyan image, the magenta image,and the yellow image were evaluated by using the R data, the G data, andthe B data, respectively.

A: The average of the area percentages of the toner that spreads is lessthan 5.0% (dot spread performance: most excellent).

B: The average of the area percentages of the toner that spreads is 5.0%or more and less than 10.0% (dot spread performance: excellent).

C: The average of the area percentages of the toner that spreads is10.0% or more and less than 15.0% (dot spread performance: good).

D: The average of the area percentages of the toner that spreads is15.0% or more (dot spread performance: poor).

(Dot Chipping)

A toner height on a drum or on unfixed paper is measured by the sameprocedure as that described above, the area of the square is defined as100%, and the area of a portion where no toner is present in the squareis measured in a percentage unit. The same operation was performed for30 randomly sampled images, and evaluation for dot chipping wasperformed by determining the average of the areas. Evaluation criteriaare shown below. FIG. 14 shows a conceptual view of dot chipping. Itshould be noted that, for each of a cyan image, a magenta image, and ayellow image, data on an observed image was divided into red (R), green(G), and blue (B), and the cyan image, the magenta image, and the yellowimage were evaluated by using the R data, the G data, and the B data,respectively.

A: The average of the area percentages of portions where no toner ispresent is less than 5.0% (dot chipping performance: most excellent).

B: The average of the area percentages of portions where no toner ispresent is 5.0% or more and less than 10.0% (dot chipping performance:excellent).

C: The average of the area percentages of portions where no toner ispresent is 10.0% or more and less than 15.0% (dot chipping performance:good).

D: The average of the area percentages of portions where no toner ispresent is 15.0% or more (dot chipping performance: poor).

Examples 2 to 20 and Comparative Examples 1 to 21

Evaluation was performed in the same manner as in Example 1 except thatany toner shown in Table 17 was used. It should be noted that image databased on a CIELAB color coordinate system with (L*=47.0, a*=75.0,b*=−6.0) (magenta solid image specified as a Japan color) was used asdata on an image to be evaluated in each of Examples 6 to 10 andComparative Examples 6 to 10, image data based on the CIELAB colorcoordinate system with (L*=88.0, a*=−6.0, b*=95.0) (yellow solid imagespecified as a Japan color) was used as data on an image to be evaluatedin each of Examples 11 to 15 and Comparative Examples 11 to 15, andimage data based on the CIELAB color coordinate system with (L*=13.2,a*=1.3, b*=1.9) (black solid image specified as a Japan color) was usedas data on an image to be evaluated in each of Examples 16 to 20 andComparative Examples 16 to 21. In addition, Tables 18 to 21 show theresults.

TABLE 17 Cyan Magenta Yellow Example developer developer developer Blackdeveloper Example 1 Cyan toner 1 Magenta toner 4 Yellow toner 4 Blacktoner 4 Example 2 Cyan toner 2 Magenta toner 4 Yellow toner 4 Blacktoner 4 Example 3 Cyan toner 3 Magenta toner 4 Yellow toner 4 Blacktoner 4 Comparative Example 1 Cyan toner 4 Magenta toner 4 Yellow toner4 Black toner 4 Comparative Example 2 Cyan toner 5 Magenta toner 4Yellow toner 4 Black toner 4 Example 4 Cyan toner 6 Magenta toner 4Yellow toner 4 Black toner 4 Example 5 Cyan toner 7 Magenta toner 4Yellow toner 4 Black toner 4 Comparative Example 3 Cyan toner 8 Magentatoner 4 Yellow toner 4 Black toner 4 Comparative Example 4 Cyan toner 9Magenta toner 4 Yellow toner 4 Black toner 4 Comparative Example 5 Cyantoner 10 Magenta toner 4 Yellow toner 4 Black toner 4 Example 6 Cyantoner 4 Magenta toner 1 Yellow toner 4 Black toner 4 Example 7 Cyantoner 4 Magenta toner 2 Yellow toner 4 Black toner 4 Example 8 Cyantoner 4 Magenta toner 3 Yellow toner 4 Black toner 4 Comparative Example6 Cyan toner 4 Magenta toner 4 Yellow toner 4 Black toner 4 ComparativeExample 7 Cyan toner 4 Magenta toner 5 Yellow toner 4 Black toner 4Example 9 Cyan toner 4 Magenta toner 6 Yellow toner 4 Black toner 4Example 10 Cyan toner 4 Magenta toner 7 Yellow toner 4 Black toner 4Comparative Example 8 Cyan toner 4 Magenta toner 8 Yellow toner 4 Blacktoner 4 Comparative Example 9 Cyan toner 4 Magenta toner 9 Yellow toner4 Black toner 4 Comparative Example 10 Cyan toner 4 Magenta toner 10Yellow toner 4 Black toner 4 Example 11 Cyan toner 4 Magenta toner 4Yellow toner 1 Black toner 4 Example 12 Cyan toner 4 Magenta toner 4Yellow toner 2 Black toner 4 Example 13 Cyan toner 4 Magenta toner 4Yellow toner 3 Black toner 4 Comparative Example 11 Cyan toner 4 Magentatoner 4 Yellow toner 4 Black toner 4 Comparative Example 12 Cyan toner 4Magenta toner 4 Yellow toner 5 Black toner 4 Example 14 Cyan toner 4Magenta toner 4 Yellow toner 6 Black toner 4 Example 15 Cyan toner 4Magenta toner 4 Yellow toner 7 Black toner 4 Comparative Example 13 Cyantoner 4 Magenta toner 4 Yellow toner 8 Black toner 4 Comparative Example14 Cyan toner 4 Magenta toner 4 Yellow toner 9 Black toner 4 ComparativeExample 15 Cyan toner 4 Magenta toner 4 Yellow toner 10 Black toner 4Example 16 Cyan toner 4 Magenta toner 4 Yellow toner 4 Black toner 1Example 17 Cyan toner 4 Magenta toner 4 Yellow toner 4 Black toner 2Example 18 Cyan toner 4 Magenta toner 4 Yellow toner 4 Black toner 3Comparative Example 16 Cyan toner 4 Magenta toner 4 Yellow toner 4 Blacktoner 4 Comparative Example 17 Cyan toner 4 Magenta toner 4 Yellow toner4 Black toner 5 Comparative Example 18 Cyan toner 4 Magenta toner 4Yellow toner 4 Black toner 6 Example 19 Cyan toner 4 Magenta toner 4Yellow toner 4 Black toner 7 Example 20 Cyan toner 4 Magenta toner 4Yellow toner 4 Black toner 8 Comparative Example 19 Cyan toner 4 Magentatoner 4 Yellow toner 4 Black toner 9 Comparative Example 20 Cyan toner 4Magenta toner 4 Yellow toner 4 Black toner 10 Comparative Example 21Cyan toner 4 Magenta toner 4 Yellow toner 4 Black toner 11

TABLE 18 Toner amount Ml_(C) Low High on transfer Q_(C)/A_(C620) 80%non-off set non-off set material First 3,000-th 6,000-th toner heightH_(C80)/ temperature temperature Example (mg/cm²) A_(C)620 A_(C) sheetsheet sheet (μm) H_(C20) (° C.) (° C.) Example 1 0.24 1.907 7.2 40.940.9 39.9 12 1.09 120 200 Example 2 0.18 2.051 10.4 44.4 42.9 41.9 101.11 120 190 Example 3 0.35 1.741 4.5 32.2 31.6 30.4 14 1.17 120 200Comparative 0.52 1.340 2.3 21.6 21.6 20.9 22 1.59 120 160 Example 1Comparative 0.25 1.765 6.4 44.8 40.2 32.3 15 1.26 110 140 Example 2Example 4 0.26 1.882 5.8 38.3 37.2 35.1 13 1.10 130 220 Example 5 0.381.593 3.4 30.1 28.2 24.5 16 1.18 130 220 Comparative 0.26 1.779 5.5 39.336.5 29.2 16 1.32 130 220 Example 3 Comparative 0.37 1.286 2.8 38.1 28.720.2 18 1.44 120 150 Example 4 Comparative 0.14 1.760 10.1 52.3 47.732.4 9 1.13 150 220 Example 5 Charge quantity (mC/kg) Dot spread Dotchipping Gloss uniformity Color First 3,000-th 6,000-th First 3,000-th6,000-th First 3,000-th 6,000-th First 3,000-th 6,000-th Example spacesheet sheet sheet sheet sheet sheet sheet sheet sheet sheet sheet sheetExample 1 A 78 78 76 A A A A A A A A A Example 2 B 91 88 86 A A A A B BA A B Example 3 A 56 55 53 B B B A A B A A A Comparative — 29 29 28 C CC A A A A A A Example 1 Comparative D 79 71 57 A A B A B C C C C Example2 Example 4 A 72 70 66 A B B B B C A B C Example 5 A 48 45 39 B B C A BB A B B Comparative D 70 65 52 A B B B C C A C C Example 3 Comparative C49 33 26 B B C A B C C C C Example 4 Comparative D 92 84 57 A B C C C DB B C Example 5

TABLE 19 Toner amount Ml_(M) Low High on transfer Q_(M)/A_(M570) 80%non-off set non-off set material First 3,000-th 6,000-th toner heightH_(C80)/ temperature temperature Example (mg/cm²) A_(M)570 A_(M) sheetsheet sheet (μm) H_(C20) (° C.) (° C.) Example 6 0.23 1.972 7.8 40.640.6 39.6 12 1.09 120 200 Example 7 0.18 2.113 10.7 44.0 42.1 41.2 101.11 120 190 Example 8 0.34 1.904 5.1 30.5 29.9 28.9 14 1.16 120 200Comparative 0.53 1.521 2.6 20.4 20.4 19.7 22 1.57 120 160 Example 6Comparative 0.25 1.714 6.2 47.3 42.0 35.0 15 1.25 110 140 Example 7Example 9 0.26 2.038 6.3 36.3 35.8 33.4 13 1.10 130 220 Example 10 0.371.670 3.6 29.9 28.1 24.6 16 1.17 130 220 Comparative 0.26 1.749 5.4 41.738.3 31.4 16 1.31 130 220 Example 8 Comparative 0.38 1.526 3.2 33.4 22.918.3 18 1.42 120 150 Example 9 Comparative 0.14 1.762 10.1 53.3 48.833.5 9 1.12 150 220 Example 10 Charge quantity (mC/kg) Dot spread Dotchipping Gloss uniformity Color First 3,000-th 6,000-th First 3,000-th6,000-th First 3,000-th 6,000-th First 3,000-th 6,000-th Example spacesheet sheet sheet sheet sheet sheet sheet sheet sheet sheet sheet sheetExample 6 A 80 80 78 A A A A A A A A A Example 7 B 93 89 67 A A A A B BA A B Example 8 A 58 57 55 B B B A A B A A A Comparative — 31 31 30 C CC A A A A A A Example 6 Comparative D 81 72 60 A A B A B C C C C Example7 Example 9 A 74 73 68 A B B B B C A B C Example 10 A 50 47 41 B B C A BB A B B Comparative D 73 67 55 A B B B C C A C C Example 8 Comparative C51 35 28 B B C A B C C C C Example 9 Comparative D 94 86 59 A B C C C DB B C Example 10

TABLE 20 Toner amount Ml_(Y) Low High on transfer Q_(Y)/A_(Y450) 80%non-offset non-offset material First 3,000-th 6,000-th toner heightH_(C80)/ temperature temperature Example (mg/cm²) A_(Y)450 A_(Y) sheetsheet sheet (μm) H_(C20) (° C.) (° C.) Example 11 0.25 1.852 6.7 43.743.7 42.7 12 1.08 120 200 Example 12 0.19 2.046 9.8 45.9 44.0 43.0 101.10 120 190 Example 13 0.34 1.745 4.7 33.8 33.2 32.7 14 1.15 120 200Comparative 0.52 1.560 2.7 21.2 21.2 20.5 22 1.54 120 160 Example 11Comparative 0.26 1.718 6.0 47.7 43.1 36.1 15 1.24 110 140 Example 12Example 14 0.25 1.835 5.9 40.9 40.3 37.6 13 1.09 130 220 Example 15 0.391.663 3.4 31.3 29.5 25.3 16 1.17 130 220 Comparative 0.27 1.690 5.0 43.840.2 33.7 16 1.30 130 220 Example 13 Comparative 0.37 1.627 3.5 32.022.1 17.8 18 1.39 120 150 Example 14 Comparative 0.13 1.748 10.8 54.950.3 34.3 9 1.11 150 220 Example 15 Charge quantity (mC/kg) Dot spreadDot chipping Gloss uniformity Color First 3,000-th 6,000-th First3,000-th 6,000-th First 3,000-th 6,000-th First 3,000-th 6,000-thExample space sheet sheet sheet sheet sheet sheet sheet sheet sheetsheet sheet sheet Example 11 A 81 81 79 A A A A A A A A A Example 12 A94 90 88 A A A A B B A A B Example 13 A 59 58 57 B B B A A B A A AComparative — 33 33 32 C C C A A A A A A Example 11 Comparative D 82 7462 A A B A B C C C C Example 12 Example 14 A 75 74 69 A B B B B C A B CExample 15 A 52 49 42 B B C A B B A B B Comparative D 74 68 57 A B B B CC A C C Example 13 Comparative D 52 36 29 B B C A B C C C C Example 14Comparative C 96 88 60 A B C C C D B B C Example 15

TABLE 21 Toner amount Ml_(K) Low High on transfer Q_(K)/A_(K600) 80%non-offset non-offset material First 3,000-th 6,000-th toner heightH_(C80)/ temperature temperature Example (mg/cm²) A_(K)600 A_(K) sheetsheet sheet (μm) H_(C20) (° C.) (° C.) Example 16 0.23 1.763 7.0 43.743.1 42.5 12 1.10 120 200 Example 17 0.17 1.883 10.1 48.3 46.7 45.7 101.12 120 190 Example 18 0.34 1.714 4.6 32.7 32.1 31.5 14 1.18 120 200Comparative 0.51 1.577 2.8 19.0 18.4 17.8 22 1.58 120 160 Example 16Comparative 0.24 1.639 6.2 48.2 42.7 35.4 15 1.26 110 150 Example 17Comparative 0.17 1.883 8.9 47.3 42.0 28.1 13 1.29 110 140 Example 18Example 19 0.25 1.788 5.7 40.3 39.7 36.9 13 1.11 130 220 Example 20 0.371.675 3.6 28.7 27.5 23.3 16 1.19 130 220 Comparative 0.25 1.766 5.7 40.236.8 30.6 16 1.32 130 220 Example 19 Comparative 0.36 1.643 3.7 29.820.1 15.2 18 1.43 120 150 Example 20 Comparative 0.12 1.951 13.0 46.641.5 27.2 9 1.14 150 220 Example 21 Charge quantity (mC/kg) Dot spreadDot chipping Gloss uniformity Color First 3,000-th 6,000-th First3,000-th 6,000-th First 3,000-th 6,000-th First 3,000-th 6,000-thExample space sheet sheet sheet sheet sheet sheet sheet sheet sheetsheet sheet sheet Example 16 A 77 76 75 A A A A A A A A A Example 17 A91 88 86 A A A A B B A A B Example 18 A 56 55 54 B B B A A B A A AComparative — 30 29 28 C C C A A A A A A Example 16 Comparative B 79 7058 A A B A B C C C C Example 17 Comparative C 89 79 53 A B C B C C C C CExample 18 Example 19 A 72 71 66 A B B B B C A B C Example 20 A 48 46 39B B C A B B A B B Comparative C 71 65 54 A B B B C C A C C Example 19Comparative B 49 33 25 B B C A B C C C C Example 20 Comparative C 91 8153 A B C C C D B B C Example 21

Examples 21 to 24

In each of Examples 21 to 24, evaluation was performed in the samemanner as in each of Examples 1, 6, 11, and 16, respectively exceptthat: the carrier to be used in each of Examples 1, 6, 11, and 16 waschanged to Carrier 2; and a mixing ratio between a toner and the carrierwas 4 parts by mass: 96 parts by mass. Table 22 shows the results.

TABLE 22 Dot spread Dot chipping Solid uniformity Toner used 3,000-6,000- 3,000- 6,000- 3,000- 6,000- Cyan Magenta Yellow Black First th thFirst th th First th th Example developer developer developer developersheet sheet sheet sheet sheet sheet sheet sheet sheet Example CyanMagenta Yellow Black B B C A A B A A B 21 toner 1 toner 4 toner 4 toner4 Example Cyan Magenta Yellow Black B B C A A B A A B 22 toner 4 toner 1toner 4 toner 4 Example Cyan Magenta Yellow Black B B C A A B A A B 23toner 4 toner 4 toner 1 toner 4 Example Cyan Magenta Yellow Black B B CA A B A A B 24 toner 4 toner 4 toner 4 toner 1

Example 25

Cyan Toner 1, Magenta Toner 1, Yellow Toner 1, and Black Toner 1 wereeach independently mixed with Carrier 1, and the produced two-componentdevelopers were set in the developing devices of the full-color copyingmachine used in Example 1 corresponding to the respective colors. Amixing ratio between each toner and the carrier was 8 parts by mass:92parts by mass.

The temperature of the fixing unit of the machine was set to 140° C.,and full-color images were output on 5,000 sheets of coat paper (52g/m², whiteness 83 to 84%, A4 size). A toner consumption after printingon the 5,000 sheets was determined in a percentage unit when the tonerconsumption of Comparative Example 25 was defined as 100. Evaluationcriteria are shown below. Table 24 shows the results of the evaluation.

(Color Space)

A full-color image with a 256-step gradation was formed, and its colorspace volume was evaluated as a relative value when the color spacevolume of Comparative Example 25 to be described later was defined as100%.

A: The color space volume is 96% or more of the area of ComparativeExample 25 (color space performance: most excellent).

B: The color space volume is 90% or more and less than 96% of the areaof Comparative Example 25 (color space performance: excellent).

C: The color space volume is 80% or more and less than 90% of the areaof Comparative Example 25 (color space performance: good).

D: The color space volume is less than 80% of the area of ComparativeExample 25 (color space performance: poor).

(Image Appearance of Five-Point Letter)

A five-point letter was observed with a digital microscope (VH-7000Cmanufactured by KEYENCE CORPORATION) and a lens having a magnificationof 150. It should be noted that, for each of a cyan image, a magentaimage, and a yellow image, data on an observed image was divided intored (R), green (G), and blue (B), and the cyan image, the magenta image,and the yellow image were evaluated by using the R data, the G data, andthe B data, respectively.

A: The reproducibility of each of an edge portion and a fine portion isparticularly good.

B: The reproducibility of each of an edge portion and a fine portion isgood.

C: The reproducibility is at an ordinary level.

D: The reproducibility of each of an edge portion and a fine portion ispoor.

(Gloss Uniformity)

A difference in gloss between an image portion and a non-image portionwas evaluated.

A: The maximum of the difference in gloss is less than 20 (glossuniformity: most excellent).

B: The maximum of the difference in gloss is 20 or more and less than 30(gloss uniformity: excellent).

C: The maximum of the difference in gloss is 30 or more and less than 45(gloss uniformity: good).

D: The maximum of the difference in gloss is 45 or more (glossuniformity: poor).

Examples 26 to 29 and Comparative Examples 25 to 29

Evaluation was performed in the same manner as in Example 25 except thatany toner shown in Table 23 was used. Table 24 shows the results.

TABLE 23 Example Cyan toner Magenta toner Yellow toner Black tonerExample 25 Cyan toner 1 Magenta toner 1 Yellow toner 1 Black toner 1Example 26 Cyan toner 2 Magenta toner 2 Yellow toner 2 Black toner 2Example 27 Cyan toner 3 Magenta toner 3 Yellow toner 3 Black toner 3Comparative Example 25 Cyan toner 4 Magenta toner 4 Yellow toner 4 Blacktoner 4 Comparative Example 26 Cyan toner 5 Magenta toner 5 Yellow toner5 Black toner 5 Example 28 Cyan toner 6 Magenta toner 6 Yellow toner 6Black toner 7 Example 29 Cyan toner 7 Magenta toner 7 Yellow toner 7Black toner 8 Comparative Example 27 Cyan toner 8 Magenta toner 8 Yellowtoner 8 Black toner 9 Comparative Example 28 Cyan toner 9 Magenta toner9 Yellow toner 9 Black toner 10 Comparative Example 29 Cyan toner 10Magenta toner 10 Yellow toner 10 Black toner 11

TABLE 24 Cyan developer Magenta developer Yellow developer Blackdeveloper Q_(C)/ H_(C80)/ Q_(M)/ H_(M80)/ Q_(Y)/ H_(Y80)/ Q_(K)/H_(K80)/ Example A_(C) A_(C620) H_(C20) A_(M) A_(M570) H_(M20) A_(Y)A_(Y450) H_(Y20) A_(K) A_(K600) H_(K20) Example 25 7.3 41.0 1.09 7.940.7 1.09 6.8 43.8 1.08 7.1 43.8 1.10 Example 26 10.5 44.5 1.11 10.844.1 1.11 9.9 46.0 1.10 10.2 48.4 1.12 Example 27 4.6 32.3 1.17 5.2 30.61.16 4.8 33.9 1.15 4.7 32.8 1.18 Comparative 2.4 21.7 1.59 2.7 20.5 1.572.8 21.3 1.54 2.9 19.1 1.58 Example 25 Comparative 6.5 44.9 1.26 6.347.4 1.25 6.1 47.8 1.24 6.3 48.3 1.26 Example 26 Example 28 5.9 38.41.10 6.4 36.4 1.10 6.0 41.0 1.09 5.8 40.4 1.11 Example 29 3.5 30.2 1.183.7 30.0 1.17 3.5 31.4 1.17 3.7 28.8 1.19 Comparative 5.6 39.4 1.32 5.541.8 1.31 5.1 43.9 1.30 5.8 40.3 1.32 Example 27 Comparative 2.9 38.21.44 3.3 33.5 1.42 3.6 32.1 1.39 3.8 29.9 1.43 Example 28 Comparative10.2 52.4 1.13 10.2 53.4 1.12 10.9 55.0 1.11 13.1 46.7 1.14 Example 29Toner consumption Gloss Image appearance of letter represented inExample Color space uniformity First sheet 5,000-th sheet percentageunit (%) Example 25 A B A A 38 Example 26 B A A A 30 Example 27 A C B B51 Comparative — D C C 100 Example 25 Comparative C A B C 39 Example 26Example 28 A B A B 41 Example 29 A C B C 59 Comparative D B B D 42Example 27 Comparative C A C D 60 Example 28 Comparative C A B D 20Example 29

Example 30

Cyan Toner 1, Magenta Toner 1, Yellow Toner 1, and Black Toner 1 wereset in the cyan cartridge, magenta cartridge, yellow cartridge, andblack cartridge of a commercially available color laser beam printer(LBP-5500; manufactured by Canon Inc.) corresponding to the respectivecolors. The temperature of the fixing unit of the printer was set to150° C., and a full-color image was output on recycled paper (A4-sizerecycle paper (66 g/m²), manufactured by Canon Inc.). Table 26 shows theresults of the evaluation.

(Color Gamut)

Color gamut area was evaluated with fixed images of a primary color andsecondary color when the color gamut area of Comparative Example 30 tobe described later was defined as 100%.

A: The color gamut area is 95% or more of the area of ComparativeExample 30 (color gamut performance: most excellent).

B: The color gamut area is 90% or more and less than 95% of the area ofComparative Example 30 (color gamut performance: excellent).

C: The color gamut area is 85% or more and less than 90% of the area ofComparative Example 30 (color gamut performance: good).

D: The gamut area is less than 85% of the area of Comparative Example 30(color gamut performance: poor).

(Gloss Uniformity)

A difference in gloss between a solid image portion at a front endportion and a solid image portion at a rear end portion was measured forthe direction in which paper was passed.

A: The difference in gloss is less than 5 (gloss uniformity: mostexcellent).

B: The difference in gloss is 5 or more and less than 10 (glossuniformity: excellent).

C: The difference in gloss is 10 or more and less than 15 (glossuniformity: good).

D: The difference in gloss is 15 or more (gloss uniformity: poor).

(Penetrating Performance)

A black solid image was formed on paper, and the paper was placed on awhite plate having an L* of 100 with the back surface of the paperfacing upward. The reflection density of a portion corresponding to animage portion was measured from the back surface of the paper.

A: The image density is less than 0.2 (penetrating performance: mostexcellent).

B: The image density is 0.2 or more and less than 0.3 (penetratingperformance: excellent).

C: The image density is 0.3 or more and less than 0.4 (penetratingperformance: good).

D: The image density is 0.4 or more (penetrating performance: poor).

(Image Appearance of Six-Point Letter)

A six-point letter was observed with a digital microscope (VH-7000Cmanufactured by KEYENCE CORPORATION) and a lens having a magnificationof 150. It should be noted that, for each of a cyan image, a magentaimage, and a yellow image, data on an observed image was divided intored (R), green (G), and blue (B), and the cyan image, the magenta image,and the yellow image were evaluated by using the R data, the G data, andthe B data, respectively.

A: The reproducibility of each of an edge portion and a fine portion isparticularly good.

B: The reproducibility of each of an edge portion and a fine portion isgood.

C: The reproducibility is at an ordinary level.

D: The reproducibility of each of an edge portion and a fine portion ispoor.

Examples 31 and 32, and Comparative Examples 30 and 31

Evaluation was performed in the same manner as in Example 30 except thatany toner shown in Table 25 was used. Table 26 shows the results of theevaluation.

TABLE 25 Cyan Magenta Yellow Black Example cartridge cartridge cartridgecartridge Example 30 Cyan toner 1 Magenta Yellow toner 1 Black toner 1toner 1 Example 31 Cyan toner 2 Magenta Yellow toner 2 Black toner 2toner 2 Example 32 Cyan toner 3 Magenta Yellow toner 3 Black toner 3toner 3 Comparative Cyan toner 4 Magenta Yellow toner 4 Black toner 4Example 30 toner 4 Comparative Cyan toner 5 Magenta Yellow toner 5 Blacktoner 5 Example 31 toner 5

TABLE 26 Cyan cartridge Magenta cartridge Yellow cartridge Blackcartridge Q_(C)/ H_(C80)/ Q_(M)/ H_(M80)/ Q_(Y)/ H_(Y80)/ Q_(K)/H_(K80)/ Example A_(C) A_(C620) H_(C20) A_(M) A_(M570) H_(M20) A_(Y)A_(Y450) H_(Y20) A_(K) A_(K600) H_(K20) Example 30 7.9 42.0 1.08 8.541.6 1.08 7.3 44.8 1.07 7.6 43.3 1.09 Example 31 11.7 45.3 1.10 12.045.0 1.10 10.9 46.9 1.09 11.4 49.4 1.11 Example 32 4.8 33.3 1.16 5.431.5 1.15 5.0 35.0 1.14 4.9 33.8 1.17 Comparative 2.4 23.1 1.55 2.7 21.71.53 2.8 22.4 1.51 2.9 20.3 1.54 Example 30 Comparative 7.0 45.9 1.256.8 48.4 1.24 6.5 48.9 1.23 6.8 49.4 1.25 Example 31 Color GlossPenetrating Image appearance of letter Example gamut (%) uniformityperformance First sheet 3,000-th sheet Example 30 A A A A A Example 31 BA A A A Example 32 A B A B B Comparative — C B C C Example 30Comparative C D C B D Example 31

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2007-024380, filed on 2 Feb., 2007, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An image-forming method, comprising: forming a black image by forming an electrostatic latent image on an electrostatic image bearing member, and developing the electrostatic latent image with a black toner; and transferring the black image onto a transfer material, wherein: the black toner contains a binder resin and a colorant, the colorant is contained in the black toner in an amount of from 8 parts by mass to 18 parts by mass based on 100 parts by mass of the binder resin, and the colorant is dispersed in the binder resin so that the black toner has a value (c*_(K)) for c* based on a CIELAB color coordinate system of 20.0 or less, an absorbance (A_(K600)) at a wavelength of 600 nm of 1.610 or more, and a ratio (A_(K600)/A_(K460)) of A_(K600) to an absorbance (A_(K460)) at a wavelength of 460 nm of 0.970 to 1.035 in reflectance spectrophotometry, and wherein, when a true density of the black toner is represented by ρ_(TK) and a toner amount upon development of image data represented by the CIELAB color coordinate system with L*=13.2, a*=1.3, and b*=1.9 onto the transfer material is represented by M1_(K) (mg/cm²), a coloring coefficient A_(K) represented by the following expression is 3.0 to 12.0 A _(K) =A _(K600)/(M1_(K)×ρ_(TK)).
 2. A full-color image-forming method, comprising the steps of: forming each of a plurality of electrostatic images on a charged electrostatic image bearing member; developing the formed electrostatic images with toners to form toner images; transferring the formed toner images onto a transfer material; and fixing the transferred toner images to the transfer material to form fixed images, wherein: the step of forming the toner images includes a step of performing development with a first toner selected from a black toner, a cyan toner, a magenta toner, and a yellow toner to form a first toner image, a step of performing development with a second toner except the first toner selected from the black toner, the cyan toner, the magenta toner, and the yellow toner to form a second toner image, a step of performing development with a third toner except the first toner and the second toner selected from the black toner, the cyan toner, the magenta toner, and the yellow toner to form a third toner image, and a step of performing development with a fourth toner except the first toner, the second toner, and the third toner selected from the black toner, the cyan toner, the magenta toner, and the yellow toner to form a fourth toner image; the black toner contains at least a binder resin and a colorant, and the black toner has a value (c*_(K)) for c* based on a CIELAB color coordinate system of 20.0 or less, an absorbance (A_(K600)) at a wavelength of 600 nm of 1.610 or more, and a ratio (A_(K600)/A_(K460)) of A_(K600) to an absorbance (A_(K460)) at a wavelength of 460 nm of 0.970 to 1.035 in reflectance spectrophotometry; and the black toner contains the colorant of 8 to 18 parts by mass with respect to 100 parts by mass of the binder resin, and wherein, when a true density of the black toner is represented by ρ_(TK) and a toner amount upon development of image data represented by the CIELAB color coordinate system with L*=13.2, a*=1.3, and b*=1.9 onto the transfer material is represented by M1_(K) (mg/cm²) a coefficient A_(K) resented by the following expression is 3.0 to 12.0 A _(K) =A _(K600)/(M1_(K)×ρ_(TK)).
 3. A full-color image-forming method according to claim 2, wherein the step of forming the toner images includes a step of transporting the toners to a developing portion with a toner carrying member and a step of developing the electrostatic images with the toners in the developing portion, and a ratio (Q_(K)/A_(K600)) of a charge quantity (Q_(K)) (mC/kg) of the black toner on the toner carrying member in the transporting step to A_(K600) is 22.0 to 50.0.
 4. A full-color image-forming method according to claim 2, wherein, in the step of forming the toner images, a ratio (H_(K80)/H_(K20)) of an average height (H_(K80)) of a toner layer of a toner image formed on the electrostatic image bearing member for image data having a black monochromatic density of 80% to an average height (H_(K20)) of a toner layer of a toner image formed on the electrostatic image bearing member for image data having a black monochromatic density of 20% is 0.90 to 1.30.
 5. An image-forming method, comprising: forming a black image by forming an electrostatic latent image on an electrostatic image bearing member, and developing the electrostatic latent image with a black toner; and transferring the black image onto a transfer material, wherein: the black toner contains a binder resin and a colorant, the colorant is contained in the black toner in an amount of from 8 parts by mass to 18 parts by mass based on 100 parts by mass of the binder resin, and the colorant is dispersed in the binder resin so that the black toner has a value (c*_(K)) for c* based on a CIELAB color coordinate system of 20.0 or less, an absorbance (A_(K600)) at a wavelength of 600 nm of 1.610 or more, and a ratio (A_(K600)/A_(K460)) of A_(K600) to an absorbance (A_(K460)) at a wavelength of 460 nm of 0.970 to 1.035 in reflectance spectrophotometry, wherein: when an average height of a first toner layer is defined as H_(K20), where the first toner layer is formed by developing image data having black monochromatic density of 20% on the electrostatic image bearing member with the black toner, and an average height of a second toner layer is defined as H_(K80), where the second toner layer is formed by developing image date having black monochromatic density of 80% on the electrostatic image bearing member with the black toner, said step is performed so that H_(K20) and H_(K80) satisfies the following relationship: 0.90≦H _(K80) /H _(K20)≦1.30, and wherein, when a true density of the black toner is represented by ρ_(TK) and a toner amount upon development of image data represented by the CIELAB color coordinate system with L*=13.2, a*=1.3, and b*=1.9 onto the transfer material is represented by M1_(K) (mg/cm²), a coefficient A_(K) represented by the following expression is 3.0 to 12.0 A _(K) =A _(K600)/(M1_(K)×ρ_(TK)). 